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Autor(en) Sommerwerk, Kay | Woidt, Malte | Haupt, Matthias | Horst, Peter
TitelReissner–Mindlin shell implementation and energy conserving isogeometric multi-patch coupling
HerausgeberInternational Journal for Numerical Methods in Engineering, Vol. 109, Nr. 7, S. 982–1012, (2017) (Reviewed)
Erscheinungsjahr2017
Abstract
A shear-flexible isogeometric Reissner–Mindlin shell formulation using non-uniform rational B-splines basis functions is introduced, which is used for the demonstration of a coupling approach for multiple non-conforming patches. The six degrees of freedom formulation uses the exact surface normal vectors and curvature. The shell formulation is implemented in an isogeometric analysis framework for computation of structures composed of multiple geometric entities. To enable local model refinement as well as non-matching domains coupling, a conservative multi-patch approach using Lagrange multipliers for structured non-uniform rational B-splines patches is presented. Here, an additional border frame mesh is used to couple geometries during structural analyses. This frame interface approach avoids the problem of excessive con- straints when multiple patches are coupled at one point. First, the shell formulation is verified with several reference cases. Then the influence of the frame interface discretization and frame penalty stiffness on the smoothness of the results is investigated. The effects of the perturbed Lagrangian method in combination with the frame interface approach is shown. In addition, results of models with T-joint interface connections and perpendicular stiffener patches are presented.
Internet Linkhttp://onlinelibrary.wiley.com/doi/10.1002/nme.5316/abstract


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Autor(en) Schwerter, Martin | Leester-Schädel, Monika | Dietzel, Andreas
TitelWaterproof sensor system for simultaneous pressure and hot-film flow measurements
HerausgeberSensors and Actuators A: Physical, vol. 257, 2017, pp. 208-215 (Reviewed)
Erscheinungsjahr2017
Abstract
For simultaneous measurement of pressure and near surface flow conditions allowing indirect determination of wall shear stress in experimental water tunnel environment an integrated hybrid sensor system has been developed. In contrast to known approaches, which are limited to the use in gas atmosphere due to protruding electrical and fragile parts, our sensor system is waterproof shielded and embedded in epoxy resin. Furthermore an amplification circuit for the pressure signal based on a programmable gain amplifier is integrated in direct vicinity to the pressure sensor in order to minimize noise by electromagnetic disturbances. Also sensor systems with on-board digitalization of the pressure signal for direct digital read-out were realized. We present all aspects of system assembly and embedding to one waterproof module. Furthermore, read-out strategies as well as sensor test results in air and water are shown and watertightness is confirmed.
Internet Linkdx.doi.org/10.1016/j.sna.2017.02.010


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Autor(en) Sommerwerk, Kay | Krukow, Ian | Haupt, Matthias | Dinkler, Dieter
TitelStrukturentwurf und Aeroelastik von Flügeln mit aktiver Zirkulationskontrolle
HerausgeberIngenieurspiegel 10, no. 1, pp 3-5, 2017.
Erscheinungsjahr2017
Abstract
In der zivilen Luftfahrt steigt der Bedarf nach Flugreisen weiterhin ungebremst. Die prognostizierte Nachfrage kann durch die aktuell nutzbare Infrastruktur nicht bewältigt werden und ein Aus- oder Neubau dieser Flughäfen ist mit großen gesellschaftlichen und politischen Hindernissen verbunden. Ein Lösungsansatz ist die Nutzung neuer Verkehrsmittel, die von der vorhandenen aber bislang kaum genutzten Infrastruktur profitieren können, namentlich den Kleinflughäfen mit für gängige Verkehrsflugzeuge zu kurzen Bahnlängen. Zur Nutzung dieser Flughafen werden Flugzeuge mit ausreichend hohen Kapazitäten benötigt, die die Fähigkeit besitzen, dort starten und landen zu können, dabei für wohngebietsnahe Lagen drastisch verringerten Fluglärm hervorrufen und möglichst wenig Kraftstoff verbrauchen. Dieses Konzept ermöglicht effiziente Punkt-zu-Punkt-Verbindungen, ohne das Erfordernis große Drehkreuzflughäfen anfliegen zu müssen.


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Autor(en) Mößner, Michael | Radespiel, Rolf
TitelFlow simulations over porous media - Comparisons with experiments
HerausgeberComputers and Fluids, 2017 (Reviewed)
Erscheinungsjahr2017
Abstract
A closure model is presented to compute turbulent flow over and through porous media. The model is based on the Darcy and Forchheimer term which are also applied to a Reynolds-stress turbulence model. The implementation of the model into a flow solver is validated with wind-tunnel experiments of a 2D-wing with a porous trailing edge. Pressure and PIV measurements are performed for the determination of integral force coefficients and the understanding of the detailed flow field. The measurement data are discussed and compared with the results of the numerical computations. The simulations match most of the experiments very well and reproduce the flow phenomena correctly. The remaining differences are studied in detail by parameter variations in order to understand the flow phenomena. The results yield confidence for using the closure model with minor modifications for more general applications.


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Autor(en) Atalayer, Caglar | Friedrichs, Jens | Wulff, Detlev
TitelAerodynamic Performance Comparison Of High Power Turboprop S-Duct Intake On Channel Wing At Varying Azimuth
Herausgeber12th European Conference on Turbomachinery Fluid Dynamics & Thermodynamics ETC12, Stockholm, Sweden (Reviewed)
Erscheinungsjahr2017
Abstract
S-duct intake component for a highly loaded turboprop engine was investigated considering its installation on a channel wing of an active high-lift aircraft using computational fluid dynamics. The objective is to observe the interaction effects of the propeller-nacelle-wing on the S-duct intake aerodynamics, especially when the intake is positioned at different azimuth angles with respect to rotation axis. Single scoop wrap-around type S-duct was integrated into a representative nacelle body. The propeller was modeled as an actuator disc for the slipstream effects. Steady-state Reynolds-averaged Navier-Stokes simulations were run using negative Spalart-Allmaras turbulence model. Although the results showed that the reference S-duct position at phi=270° had the relatively higher recovery than the other variations, significant improvements in total pressure distortion and intensities were achieved at phi=0° and 90° positions. Up to 3% decrease in swirl coefficient levels was observed when the wrap-around S-duct was positioned at phi=90° in comparison to reference position.
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Autor(en) Atalayer, Caglar | Friedrichs, Jens | Wulff, Detlev
TitelInstallation Effects On Highly Loaded Turboprop S-Duct Intake Proximity
HerausgeberASME Turbo Expo 2017: Turbine Technical Conference and Exposition (Reviewed)
Erscheinungsjahr2017
Abstract
S-duct intake of a highly loaded turboprop installed on a channel wing was investigated for the interaction effects using computational fluid dynamics. Performance effects on the aerodynamic interface plane (AIP) were compared for varying the intake proximity to propeller mid-plane and nacelle hub. A wrap-around intake with a length aspect ratio of L/D=3 was used for the analysis. Propeller slipstream was approximated with an actuator disc model. Steady-state RANS simulations was run for cruise condition. The performance was analysed in terms of total pressure recovery and distortion coefficients on AIP. Circumferential and radial distortion intensity descriptors were used along with standard coefficients for the distortion levels. Gain in total pressure recovery was achieved when the intake distance to nacelle hub was increased, whereas it was decreased with farther distance to actuator disc. The larger gap between the nacelle hub and the S-duct intake increased both the distortion coefficient and circumferential intensity on the AIP, as opposed to the decrease in radial distortion intensity. A different trend was observed for the intakes closest to the actuator disc, which showed higher recovery, experienced lower distortion except in radial direction. Analysis of the swirl distortion coefficient on the intake AIP revealed multiple peaks along the circumference. The comparison of maximum positive peaks confirmed a decrease with increasing distance to nacelle hub as the radial distortion intensity. The negative swirl peak comparison revealed an increase with increasing distance to nacelle hub, similar to distortion coefficient. The results will serve as guidelines for the S-duct intake design process and its integration into highly loaded turboprop nacelle of the high-lift aircraft.


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Autor(en) Schwerter, Martin | Gäding, Marcel | Leester-Schädel, Monika | Dietzel, Andreas
TitelA flexible sensor system in foil for combined absolute pressure and flow velocity measurements
HerausgeberTransducers 2017 (International Conference on Solid-State Sensors, Actuators and Microsystems), Kaohsiung, Taiwan, 2017
Erscheinungsjahr2017
Abstract
This work reports on a foil integrated, flexible pressure- and hot-film sensor system for measuring flows over curved surfaces. The miniaturized rigid silicon piezoresistive pressure transducer with enclosed reference cavity allows absolute pressure sensing. Together with a foil-based hot-film transducer both transducers are embedded in a combination of thin epoxy resin with polyimide. This in-foil sensor system is surface passive and waterproof and can be bent to a radius of 20 mm while maintaining full functionality.
Internet Linkhttp://ieeexplore.ieee.org/document/7994245/


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Autor(en) Blinstrub, Jason | Bertsch, Lothar
TitelTowards an Impact-Based Noise Reduction Method for Conceptual Aircraft Design
HerausgeberNew Results in Numerical and Experimental Fluid Mechanics X. Notes on Numerical Fluid Mechanics and Multidisciplinary Design, vol 132. Springer, Cham (Reviewed)
Erscheinungsjahr2017
Abstract
Aircraft exterior noise is typically reduced by optimizing an isolated aircraft component. The noise emission of this component is optimized with high-fidelity tools or wind tunnel measurements. However, if installed on-board of the aircraft the optimization may not have the desired effect on the total noise impact due to propagation effects or the interaction with other components. Hence, a method is presented, that derives noise reduction requirements for aircraft components based on the total aircraft noise impact. The method is implemented in a parametric aircraft noise prediction tool and applied to a reference aircraft. The aim is to use the noise requirements within conceptual aircraft design to obtain low-noise aircraft in a target-oriented way. Ultimately, this may be a first step towards a noise-to-design process.


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Autor(en) Müller, Thomas | Hennings, Holger
TitelSTRUCTURAL DYNAMIC INFLUENCE OF AN UHBR ENGINE ON A COANDA-WING
HerausgeberIFASD, Como
Erscheinungsjahr2017
Abstract
Due to the need of higher efficiency and the reduction of CO2 and noise emission the bypass ratio of gas turbines tends to increase. This leads to higher rotational masses which arises the question of gyroscopic moments influencing the eigenbehavior of the aircraft and thus the system stability regarding structural depended phenomena, e.g. flutter. Therefore this paper presents a multibody model to determine the structural coupling between a Coanda wing and an ultra high bypass ratio gas turbine (BPR of 17). The results in form of the spectral analysis of an eigenvalue analysis enables the understanding of the coupling mechanisms and gyroscopic influences. By analyzing the time dependent behavior of the wing-engine system under consid- eration of a follower force, representing the thrust, deepens the understanding of the structural load at the wing root.
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Autor(en) Giesecke, Daniel | Friedrichs, Jens | Stark, Udo
TitelPreliminary Aerodynamic Design of a Fan Stage for an Ultra High Bypass Ratio Engine
Herausgeber23rd International Society of Air-breathing Engines (ISABE) Conference, Manchester, UK, 2017 (Reviewed)
Erscheinungsjahr2017
Abstract
In the framework of the Coordinated Research Centre 880 (Sonderforschungsbereich 880) the fundamentals of an environmental friendly future regional aircraft are being developed. Therefore, an engine with a bypass ratio of 17 for the target reference aircraft mission has to be designed resulting in an increased propulsive effciency. In order to reduce the adverse viscous drag effects of a large intake for such ultra high bypass ratio engines, the intake will be reduced in its length. With this background, the engine installation position was chosen above the wing to realize some noise shielding effects as well as inflow straightening effects. To investigate the inflow situation and interaction a suitable transonic fan stage has to be developed. The paper describes the design process starting from aircraft specifications to an engine performance model and a preliminary fan stage design. The preliminary fan stage design procedure relies on the isentropic imple-radial equilibrium equation. The blade sections are parabolic mean lines with cubic thickness distributions. During the design process special attention has been drawn on the supersonic flow approaching the rotor leading edge resulting in a complex shock structure. The shock structure goes hand-in-hand with the incidence chosen. Firstly, a peak isentropic effciency of 87 percent was achieved with a large in- and outlet duct. Secondly, numerical simulations using isolated nacelle flow by cutting away the inlet duct show an increase in isentropic effciency to almost 88 percent at design point. To summarize, numerical verifications show consistent results with the design specification and hence, methodology used. Further inflow investigations in case of the on-wing mounted engine will be part of the on-going research project.


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Autor(en) Kauth, Felix | Narjes, Gerrit | Müller, Jan | Seume, Jörg | Vasista, Srinivas | Müller, Thomas | Francois, Daniela | El Sayed, Yosef | Semaan, Richard | Behr, Christian | Schwerter, Martin | Leester-Schädel, Monika | Nolte, Felix | Giesecke, Daniel | Atalayer, Caglar | Radespiel, Rolf
TitelProgress in Efficient High-Lift
HerausgeberAIAA AVIATION Forum, 35th AIAA Applied Aerodynamics Conference, Denver, 2017
Erscheinungsjahr2017
Abstract
This paper presents some of the progress in research on efficient high-lift systems for future civil aircraft achieved by the Coordinated Research Centre CRC 880 sponsored by the German Research Foundation. Several new approaches to increasing the lift are applied as part of the design of a reference aircraft with short take-off and landing ca- pability: The numerically predicted positive effect of Coanda jet blowing at the trailing edge flap is validated in water tunnel experiments. Robust miniature pressure and hot- film sensors are developed for the closed-loop control of a piezo-actuated blowing lip. A flexible leading-edge device utilizes composite materials, for which new structural designs are developed. Additionally, a potential de-icing system, as well as a lightning-strike pro- tection are presented. A high power-density electrically driven compressor with a broad operating range is designed to provide the blowing airflow. Different propulsion systems for the reference aircraft are evaluated. An ultra-high bypass ratio engine is considered to be most promising, and thus a preliminary fan stage design process is established. The rotor dynamic influences of the engine on the aircraft structure are investigated through a hybrid approach using a multibody model and modal reduction.
Internet Linkhttps://arc.aiaa.org/doi/10.2514/6.2017-3559


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Autor(en) Teichel, Sönke | Verstraete, Tom | Seume, Jörg
TitelOptimized Multidisciplinary Design of a Small Transonic Compressor for Active High-Lift Systems
HerausgeberInternational Journal of Gas Turbine, Propulsion and Power Systems, Vol. 9, No. 2, pp- 19-26 (Reviewed)
Erscheinungsjahr2017
Abstract
This paper presents the methodology and results of a design optimization of a single stage, axial compressor. At the design point, the compressor achieves a total pressure ratio of 2.33 at a mass-flow rate of 1.11 kg/s. The compressor is part of an electrically powered active high lift system (AHLS) for future civil aircraft. An automated process using numerical models to evaluate aerodynamic performances and mechanical loads due to centrifugal forces is used. This evaluation process is coupled to an evolutionary algorithm to help investigate the design-space. A parameterization strategy was developed to cover a wide design-space, excluding unreasonable de- signs. The goal was to satisfy the challenging design requirements of high pressure ratio, high power density and limited rotation speed imposed by the AHLS. The resulting design of a highly loaded com- pressor is characterized by significant end-wall slope and low blade aspect ratios, resembling a mixed flow compressor. According to CFD analysis it is predicted to cover the required operating points at total-total, polytropic efficiencies higher than 80 %.
Internet Linkhttp://www.gtsj.org/english/jgpp/v09n02tp03.pdf


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Autor(en) Rudenko, Anton | Hannig, Andre | Monner, Hans Peter | Horst, Peter
TitelExtremely deformable morphing leading edge: Optimization, design and structural testing
HerausgeberJournal of Intelligent Material Systems and Structures, DOI: 10.1177/1045389X17721036 (First Published Date: 4 August 2017) (Reviewed)
Erscheinungsjahr2017
Abstract
The future generation of high-lift devices needs to be improved to reduce the noise footprint and increase the performance for takeoff and landing of transport aircraft. To contribute to these goals, an active blown Coandă flap-based high-lift system is being investigated within the German national Collaborative Research Center 880 as an alternative to the state-of-the-art flaps. A key part of this system is an adaptive gapless droop nose with extremely large morphing deformation. The design and construction of this component are based on a structural optimization framework. The framework consists of two hierarchical design steps: an optimization of the hybrid composite skin layout with integral T-stringers, acting as joints to the inner actuation mechanism, and the kinematic optimization of the latter. A hybrid skin structure allows a large curvature to rupture in the morphing direction, while providing high stiffness in the transverse direction. This article describes a full-scale hybrid composite morphing droop nose and its structural tests. The results of these tests are finally compared to the finite element simulation and applied for validation of the optimization framework. A sensitivity analysis is provided to evaluate the influence of modelling and manufacturing uncertainties to the shape quality.
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Internet Linkhttp://journals.sagepub.com/doi/abs/10.1177/1045389X17721036


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Autor(en) Rossian, Lennart | Ewert, Roland | Delfs, Jan
TitelEvaluation of Acoustic Jump Conditions at Discontinuous Porous Interfaces
HerausgeberAIAA AVIATION 2017, Denver
Erscheinungsjahr2017
Abstract
Over the past years, the reduction of airfoil trailing edge noise has been addressed amongst others by the application of porous, permeable materials directly at the geometric edges, as these present a prominent noise source location. In experimental investigations, the beneficial influence of porous materials was found to be approximately 6 dB with a broadband nature. On the numerical side, with the approach of volume averaging a promising means to model complex porous materials has been found. Therewith, successful simulations have been run, that relate to experimental findings. In the following, an explicit modeling of the discontinuous interface between the porous material and the surrounding free flow by specific interface conditions was formulated. In the present paper an approach to evaluate different formulations of said interface conditions is presented and applied. The results are discussed concerning their physical background. Last, application simulations of a NACA0012 airfoil with solid and porous trailing edge are shown and compared to experimental data.


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Autor(en) Rossian, Lennart | Ewert, Roland | Jan, Delfs
TitelSimulation von Hinterkantenlärm an Tragflügelprofilen mit porösen Elementen
HerausgeberJahrestagung für Akustik DAGA 2017
Erscheinungsjahr2017
Abstract
Mit der erfolgreichen Reduktion von Antriebslärm heutiger Verkehrsflugzeugen gewinnt Umströmungslärm eine immer größere Bedeutung. Dieser entsteht unter anderem durch die Interaktion der Wirbelstrukturen der turbulenten Grenzschicht mit der Hinterkante der Tragflügel. Zur Reduzierung dieser Lärmquelle werden verschiedene Ansätze verfolgt, unter anderem gezackte Hinterkanten, so genannte Serrations. Ein weiterer Ansatz besteht im Einsatz von strömungsdurchlässigen, porösen Materialien. Experimentelle Untersuchungen haben bereits gezeigt, dass mit porösen Metallen eine breitbandige Lärmreduktion erreicht werden kann. Bei der numerischen Modellierung solcher Materialien im DLR CAA-Code PIANO wird auf eine volumengemittelte Beschreibung mittels charakteristischer Materialparameter zurückgegriffen. Eine besondere Modellierung wird dabei für die Ränder des porösen Materials benötigt, da hier eine Unstetigkeit beim Übergang zwischen porösem Material und freier Umströmung vorliegt. Dafür wurden akustische Sprungbedingungen formuliert, die eine Umrechnung zwischen den beiden Bereichen ermöglichen. Mit diesen Methoden ist es möglich, den Einfluss von verschiedenen Materialparametern auf den erzeugten Lärm zu untersuchen. Von besonderem Interesse ist hierbei die Betrachtung von anisotropen und gradierten Materialien.


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Autor(en) Lippitz, Nicolas | Rösler, Joachim
TitelAnalyzing the structure evolution of porous aluminum during cold rolling
HerausgeberMetFoam, Barcelona, Spanien, 2015
Erscheinungsjahr2017
Abstract
In times of increasing numbers of flights and growing airports close to residential areas, noise reduction of future airplanes is of major importance. To reduce the noise, which is dominating during landing, low-noise trailing edges of porous materials are investigated. A promising material is porous aluminum, which is produced using a salt infiltration method and available with various pore shapes and porosities. However, to meet the aeroacoustic and aerodynamic requirements ideally, adjustments of the pore shape and grade of porosity are necessary. This work investigates the possibilities to influence the porosity and pore shape of porous aluminum, using a cold rolling process. First results about the forming capability and evolution of porosity and pore morphology of porous aluminum during cold rolling are presented. For this porous aluminum was characterized for different degrees of deformation, using three-dimensional X-ray tomography.
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Autor(en)Diekmann, Jobst Henning
TitelFlight Mechanical Challenges of STOL Aircraft Using Active High-Lift
Herausgeber35. Applied Aerodynamics Conference, AVIATION 2017, Denver, CO
Erscheinungsjahr2017
Abstract
This paper focuses on the flight mechanical characteristics of an active high-lift supported transport type aircraft. The presented configuration combines a boundary-layer controlled flaps system with the benefits of propeller slipstream deflection. The underlying aerodynamic models and assumptions are provided. The extraordinary flight performances especially at low airspeed will be pointed out, as well as potential weaknesses. Special attention is paid to the unusually strong aerodynamic couplings in the lateral motion. Therefore, flight dynamics characteristics will be presented and their challenges discussed. The key influences are pointed out and an outlook will be given, how to exploit this knowledge for safe and satisfactory aircraft operation and handling.
Internet Linkhttps://arc.aiaa.org/doi/pdf/10.2514/6.2017-3561


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Autor(en) Diekmann, Jobst Henning | Keller, Dennis | Faez, Edris | Rudnik, Ralf | Gollnick, Volker
TitelFlight mechanics model for spanwise lift and rolling moment distributions of a segmented active high-lift wing
HerausgeberCEAS Aeronautical Journal (Reviewed)
Erscheinungsjahr2017
Abstract
In this study, the aerodynamics of wings using an active high-lift system are investigated. The target is the flight mechanical description of the spanwise forces and resulting moments and the influence of the active high-lift system to their distribution. The high-lift system is a blown flap system divided into six segments per wing. Each segment is assumed to be individually controlled, so the system shall be used for aircraft control and system failure management. This work presents a flight mechanical sub-model for the simulation of flight dynamics, which has been derived from high-fidelity CFD results. An assessment of single-segment blowing system failures will be presented including recommendations for compensation of either lift or rolling moment loss. For this investigation, the compensation is required to act at the same wing side on which the failure appears. Thus, the potential for an increase of system reliability shall be proven. The results show that less performance investment in terms of pressurized air is necessary to compensate the rolling moment of a failing segment instead of its lift. However, large blowing performance increases for the remaining wing segments that occur for some of the failure cases.
Internet Linkhttps://link.springer.com/article/10.1007/s13272-017-0261-4


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Autor(en) Müller, Jan | Mertens, Axel
TitelPower Electronics Design for a direct-driven Turbo Compressor Used as Advanced High-Lift System in Future Aircraft
HerausgeberIECON, Peking, 2017 (Reviewed)
Erscheinungsjahr2017
Abstract
This paper presents the 100kW air-cooled inverter design of a power train used for advanced high-lift systems in future aircrafts. To achieve additional high-lift during take-off and landing of a plane, air is blown out at the back flap of the wings using a turbo compressor directly driven by an electrical machine. Silicon Carbide (SiC) devices promise large savings in volume, weight and losses of the inverter, which results in a highly-integrated system. Furthermore, the intake air is used as coolant for the power electronics. Such a system with a high power density of 10.8 kW/l has been designed and implemented, and first tests were performed on a laboratory prototype.


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Autor(en) Narjes, Gerrit | Müller, Jan | Kauth, Felix | Seume, Jörg | Mertens, Axel | Ponick, Bernd
TitelKompakte elektrisch angetriebene Turbokompressoren für ein aktives Hochauftriebssystem künftiger Verkehrsflugzeuge
HerausgeberE-MOTIVE Expertenform, Hannover, Deutschland, 2017
Erscheinungsjahr2017
Abstract
Steigende Passagierzahlen in der zivilen Luftfahrt gekoppelt mit den wachsenden Anforderungen an Flugzeuge hinsichtlich Schallemissionsreduzierung im Bereich des Flughafens erfordern die Untersuchung neuartiger Konzepte zur Erzeugung des Auftriebs. Der Sonderforschungsbereich 880 befasst sich mit verschiedenen Themenbereichen um die Lärmbelastung und den Treibstoffverbrauch künftiger Flugzeugtypen zu reduzieren. Ein Ansatz, der untersucht wird, stellt die Nutzung eines aktiven Hochauftriebssystems dar, das durch eine Kombination aus Grenzflächenabsaugung an der Tragflächenoberseite und Ausblasung an den hinteren Klappen durch Nutzung des Coanda-Effekts eine Steigerung des Auftriebs ermöglicht. Die Realisierung erfolgt durch sechs Kompressorsysteme pro Tragfläche, die aus einem Umrichter, einer permanentmagneterregten Synchronmaschine und einem Turbokompressor bestehen. Zur Reduzierung des benötigten Volumens und des Gewichts wird auf ein Getriebe verzichtet, was zu einer Anwendung mit hohen Drehzahlen und hohen Frequenzen führt. Zusätzlich dient lediglich die angesaugte Luft als Kühlmedium, um zusätzliche eingebrachte Masse durch ein Kühlsystem zu vermeiden. Die Leistungselektronik nutzt ein neuartiges Aufbaukonzept und erreicht eine Leistungsdichte von 10,8 kW/l beim Wechselrichter. Zusätzlich werden Silizium-Karbid-Halbleitermodule eingesetzt um die benötigten hohen Ausgangsfrequenzen zu realisieren und die Verlustleistung zu minimieren. Der Turbokompressor wird mit Hilfe automatisierter Optimierungsmethoden dimensioniert, was zu einem einstufigen Axialverdichter führt, der den erforderlichen Coanda-Strahl bereitstellt. Die elektrische Maschine treibt den Kompressor bei 60.000 min-1 mit einer Leistung von 80 kW an. Solch hohe Drehzahlen erfordern eine genaue Betrachtung der Rotormechanik und stellen hohe Ansprüche an die thermische Vorausberechnung. Da es sich um eine Flugzeuganwendung handelt geschieht die Dimensionierung für eine Kühlmediumtemperatur von 50 °C, um die Umgebungstemperaturen in wärmeren Regionen zu berücksichtigen. Durch das Hochdrehzahlkonzept und eine Auslegung im S2 Betrieb konnte eine Leistungsdichte des Motoraktivteils von 7 kW/kg erreicht werden. Dieser Beitrag soll die Komponenten des aktiven Hochauftriebssystems im Einzelnen vorstellen und einen Überblick über die Dimensionierung eines solchen Gesamtsystems liefern. Dies umfasst ebenfalls die während des Dimensionerungsprozesses entwickelte ganzheitliche Auslegungsmethodik.


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Autor(en)Pierzyna, Maximilian
TitelTest
HerausgeberTest
Erscheinungsjahr2017
Abstract
Abstract


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Autor(en) Schwerter, Martin | Gräbner, Daniel | Hecht, Lars | Vierheller, Anke | Leester-Schädel, Monika | Dietzel, Andreas
TitelSurface-Passive Pressure Sensor by Femtosecond Laser Glass Structuring for Flip-Chip-in-Foil Integration
HerausgeberJournal of Microelectromechanical Systems, ISSN 1057-7157, vol. 25, no. 3, IEEE , pp. 517-523, 2016 (Reviewed)
Erscheinungsjahr2016
Abstract
To allow for smaller sizes, smoothness and robustness of exposed surface, and for integration in flexible sensor arrays, an innovative piezoresistive pressure sensor design has been developed. In contrast to known concepts, the sensing elements and the conducting tracks are positioned within the pressure reference chamber and, thus, protected against environmental influences such as water or particles. Sensing elements are electrically accessible from the backside by vias, thus enabling a fully flat surface totally free of electrical elements as desired for flow experiments. The sensor comprises a thin silicon sensing membrane and a body made from glass holding the reference chamber and the vias. The structuring of the sensor body is performed by femtosecond laser ablation. Steep ablation edges are realized, leading to small sensor dimensions. The sensing membrane is fabricated using potassium hydroxide (KOH) wet etching. The glass body and the silicon membrane can be connected with different techniques; hitherto, adhesive bonding by an epoxy resin layer was successfully tested. A sensitivity of 10 mV/V/bar and stable operation up to 7 bar absolute pressure could already be demonstrated. The new concept simplifies micromanufacture and allows for flip-chip-assembly in foil-based flexible systems that can be used in liquids and harsh environments.
Internet Linkhttp://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=7438755


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Autor(en) Woidt, Malte | Sommerwerk, Kay | Haupt, Matthias | Horst, Peter
TitelMODELLING STIFFENED LIGHTWEIGHT STRUCTURES WITH ISOGEOMETRIC ANALYSIS VIA MORTAR METHODS
HerausgeberECCOMAS Congress 2016, VII European Congress on Computational Methods in Applied Sciences and Engineering, Crete Island, Greece, 5–10 June 2016
Erscheinungsjahr2016
Abstract
A method to model stiffened panels with NURBS-based isogeometric analysis is presented. Stiffeners and panel are modeled as separate patches and coupled by Mortar methods. The stiffeners and panel meshes can be non-conforming. Therefore modeling of the geometry is simple even with the NURB’s limitation to structured meshes. The feasibility of the method is shown for static and modal analyses. The method is validated against results obtained from standard finite element approaches with conforming meshes for a panel with one stiffener and a panel with multiple stiffeners. For all cases good accordance to the FEM results is observed with a difference of less than 1%.


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Autor(en) Sommerwerk, Kay | Haupt, Matthias
TitelHochauftrieb künftiger Verkehrsflugzeuge – Strukturentwurf und Aeroelastik: Aeroelastische Analysen von Flügeln mit aktiver Zirkulationskontrolle
HerausgeberHLRN Informationen, 19, 2-4
Erscheinungsjahr2016
Abstract
Im Rahmen des Sonderforschungsbereichs (SFB) 880 „Grundlagen des Hochauftriebs künftiger Verkehrsflugzeuge“ werden Forschungen zum effizienten Hochauftrieb, den Effekten auf die Aeroakustik sowie der Flugdynamik durchgeführt. Als Grundlage der Forschung und der Technologiebewertung werden die verfolgten Ansätze und Ideen an einem potentiellen Flugzeug geprüft. Im Rahmen des SFB 880, Teilprojekt „Strukturentwurf und Aeroelastik“ werden die wesentlichen Phänomene des aeroelastischen Verhaltens analysiert und Entwurfskonzepte entwickelt. Es gilt sowohl das globale Trag- und Schwingungsverhalten des Tragflügels einschließlich der Phänomene der Zirkulations- und Ruderumkehr, des Low-Speed-Flatterns und der Torsionsdivergenz, als auch das lokale Verhalten – Deformationen der Coandă-Klappen und des Ausblasespaltes – zu untersuchen.


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Autor(en) Sommerwerk, Kay | Michels, Benedikt | Lindhorst, Klemens | Haupt, Matthias | Horst, Peter
TitelApplication of efficient surrogate modeling to aeroelastic analyses of an aircraft wing
HerausgeberAerospace Science and Technology 55 (2016) 314–323 (Reviewed)
Erscheinungsjahr2016
Abstract
A nonlinear, transient surrogate model is constructed to replace the computational fluid dynamics solver within the aeroelastic analysis of a detailed aircraft wing with variable fuel tank levels during cruise flight. This surrogate model allows high-fidelity analyses at a fraction of the original computational cost with satisfactory accuracy. During the model construction a parameter reduction via proper orthogonal decomposition is combined with a radial basis function artificial network for system identification and nonlinear effects. Transient forced motion computational fluid dynamics analyses based solely on the structural dynamic behavior of the detailed wing model are used as training inputs. To assess the accuracy of the approach the reduced-order model results are compared with high-fidelity full-scale aeroelastic computations. A small local reduction in accuracy can be seen for highly nonlinear effects like dynamic shock movements. However, variations in tank fill level or angle of attack show sufficient agreement of the model with the full-scale analyses. An interpolation of an intermediary angle of attack shows higher errors due to large changes in aerodynamic phenomena between the sample points.
Internet Linkhttp://dx.doi.org/10.1016/j.ast.2016.06.011


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Autor(en) Blech, Christopher | Shi, Xiaojun | Langer, Sabine Christine
TitelÜber die Sensitivität des FRAC für eine objektive Validierung mechanischer Modelle
HerausgeberFortschritte der Akustik - DAGA 2016, ISBN 978-3-939296-10-2, 42, 859ff, DAGA, Aachen, Deutschland, 2016
Erscheinungsjahr2016
Abstract
Die Validierung von mechanischen Ersatzmodellen ist heute und in den nächsten Jahrzehnten trotz zunehmender Genauigkeit und Akzeptanz der Modelle essentiell. Beschränkt man sich auf die direkte Strukturantwort eines Systems im Frequenzbereich, so finden sich in der Literatur häufig rein optische Vergleiche von Frequenzgängen einzelner Freiheitsgrade oder Durchschnittsgrößen aus Versuch und Berechnung. Der optische Vergleich, beispielsweise zweier Eingangsadmittanzen, bestätigt jedoch aufgrund des subjektiven Einflusses keinesfalls die Validität eines gesamten mechanischen Ersatzmodells. Besser wäre die Anwendung einer objektiven Größe wie das FRAC (Frequency Response Assurance Criterion). FRAC nutzt das normierte Skalarprodukt der Vektoren zweier Frequenzgänge und erlaubt somit einen Vergleich dieser auf einer Skala von Null bis Eins für jeden definierten Freiheitsgrad des betrachteten Systems. Eine Eins stellt dabei ein identisches Systemverhalten dar. Die Interpretierbarkeit des FRAC-Wertes abseits der Extremwerte wurde bis heute in der Literatur kaum untersucht. Entsprechend beschäftigt sich dieser Beitrag mit der Sensitivität des FRAC auf Steifigkeit, Dämpfung und Masse einfacher beispielhafter Strukturen. Während die Massenverteilung hinreichend genau definiert werden kann, sind Steifigkeit und vor allem Dämpfungen meist schwerer zu bestimmen. Als Beispiel dient hier die Modellierung elastischer Randbedingungen mit Federn (anstelle zwischen einer festen Einspannung oder einer gelenkigen Lagerung zu entscheiden). Der Beitrag ermöglicht zukünftig objektive Vergleiche von Frequenzgängen und eine bessere Einschätzung eines Modells auf Basis des FRAC.


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Autor(en) Rothe, Sebastian | Blech, Christopher | Langer, Sabine Christine
TitelModel Updating Strategies in Frequency Domain For Different Use Cases
HerausgeberICSV, 23, Athens, Greece, 2016
Erscheinungsjahr2016
Abstract
In acoustics, finite element models are frequently used to simulate the dynamic response of structures. The validation of finite element models is indispensable and often supported by model updating techniques. Furthermore, the computation of structures with high modal densities or non-linearities is nearly impossible in modal space. Hence, the simulation in frequency domain is preferred. In literature, many correlation criteria and updating techniques are available for the application in frequency domain. The main purpose of model updating is to find suitable modeling parameters in order to achieve a good agreement between the model and reality. Since reality is not known, often experimental data is taken as reference for the applied correlation criteria. Besides classical model updating, a lot more use cases as inverse material parameter identification, model assessment, topology optimization and shape optimization may be pursued for parameterized finite element models. It is assumed that specific adaptations of the correlation criterion and the updating technique can improve the outcome for each use case. In this contribution, strategies to combine the frequency response assurance criteria (FRAC) and an optimization algorithm are applied to different use cases. As an application example a plate structure is selected. The computational costs, the convergence behavior and the final results are evaluated for each pursued use case (e.g. model assessment). Modifications of the setup (correlation criteria or optimization algorithm) are discussed and tested for each use case to improve efficiency, robustness and the quality of results.


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Autor(en) Ring, Tobias | Blech, Christopher | Langer, Sabine Christine
TitelAn approach to evaluate the model quality using model updating Techniques
HerausgeberICSV, 23, Athens, Greece, 2016
Erscheinungsjahr2016
Abstract
The understanding of physical processes in engineering as well as in most scientific fields is based on models which are built in order to answer specific questions. The design of models for specific questions results in a limited applicability and a limited prediction accuracy. If, for example, the deflection shape of a plate-like structure shall be computed, the applied plate theory limits the accuracy of the results obtained. Giving another example, the static bending shape of a beam can be computed using a coarse discretization with reasonable accuracy. The same model may be used in order to study the dynamic behavior of the beam. Then, the ratio of wavelength and element size limits the applicability of the model. Both examples show that the accuracy of results always depends on the model, its properties and the assumptions made during the model design process. In this paper, a method is proposed, which uses a model updating technique in order to measure the quality of different models for structural dynamics. Therefore, a simple structure is modeled using approaches of different complexity. The dynamic response is compared to measurement results and the models are being updated. Different measures concerning the updating process are identified in order to evaluate the model quality. The knowledge obtained about model quality measures can be used to design models which enable higher accuracy and less necessary iterations during the model updating process a priori.


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Autor(en) Lippitz, Nicolas | Blech, Christopher | Rösler, Joachim | Langer, Sabine
TitelIdentification of Material Parameters for the Simulation of Acoustic Absorption of Fouled Sintered Fiber Felts
HerausgeberMaterials, ISSN 1996-1944, 9(8), 709, MDPI (Reviewed)
Erscheinungsjahr2016
Abstract
As a reaction to the increasing noise pollution, caused by the expansion of airports close to residential areas, porous trailing edges are investigated to reduce the aeroacoustic noise produced by flow around the airframe. Besides mechanical and acoustical investigations of porous materials, the fouling behavior of promising materials is an important aspect to estimate the performance in long-term use. For this study, two intered fiber felts were selected for a long-term fouling experiment where the development of the flow resistivity and accumulation of dirt was observed. Based on 3D structural characterizations obtained from X-ray tomography of the initial materials, acoustic models (Biot and Johnson–Champoux–Allard) in the frame of the transfer matrix method were applied to the sintered fiber felts. Flow resistivity measurements and the measurements of the absorption coefficient in an impedance tube are the basis for a fouling model for sintered fiber felts. The contribution will conclude with recommendations concerning the modeling of pollution processes of porous materials.
Internet Linkhttp://www.mdpi.com/1996-1944/9/8/709/pdf


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Autor(en) Sommerwerk, Kay | Krukow, Ian | Haupt, Matthias | Dinkler, Dieter
TitelInvestigation of Aeroelastic Effects of a Circulation Controlled Wing
HerausgeberAIAA Journal of Aircraft, Vol. 53, No. 6 (2016) (Reviewed)
Erscheinungsjahr2016
Abstract
The aeroelastic behavior of the wing of a 100-passenger aircraft under investigation in the Coordinated Research Center SFB 880 is studied. A compressed air jet upstream of the high-lift devices called the Coandă jet enables boundary layer control with delayed flow separation and consequently high lift. Aeroelastic instabilities caused by boundary layer control systems are critical to the aircraft performance. The understanding of cause and effect of these instabilities is of great importance. For analyses, a multilevel approach is pursued using full-scale three-dimensional models and reduced-order models. Both model types use fluid-structure interaction techniques. The full-scale models are used to generate a sized wing structure with realistic mass and stiffness distributions using computational fluid dynamics loads of cruise and landing configuration load cases. A reduced-order model is derived by modal reduction for computationally efficient investigations of multiple flight states. To study local aeroelastic effects and to develop three- dimensional corrections for the reduced-order model, full-scale three-dimensional coupled fluid-structure analyses are investigated. The results show that especially the dynamic behavior of wings with active circulation control may differ significantly from that of conventional wings due to the different aerodynamic behavior caused by the Coandă jet.
Internet Linkhttp://arc.aiaa.org/doi/10.2514/1.C033780


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Autor(en) Sommerwerk, Kay | Michels, Benedikt | Haupt, Matthias | Horst, Peter
TitelINVESTIGATION OF ENGINE EFFECTS ON STRUCTURAL SIZING AND STATIC AEROELASTIC SENSITIVITIES OF A CIRCULATION CONTROLLED WING
Herausgeber65. Deutscher Luft- und Raumfahrtkongress 2016, 13.-15. September 2016, Braunschweig
Erscheinungsjahr2016
Abstract
Extended configurations of a short take-off and landing aircraft under investigation at the Coordinated Research Centre SFB 880 include a morphing droop nose and a tractor propeller engine. The STOL capabilities are achieved by circulation control via a high velocity jet over the flap leading edges utilizing the Coanda effect. High-detail structural wing models are sized with a fully stressed approach using a partitioned fluid-structure interaction process. The aerodynamic part is covered by highly detailed computational fluid simulations. The effect of the engine integration on the wing mass is small but noteworthy. An aerodynamic performance assessment is conducted for the rigid and flexible wing. The influences of the model extension on the global and local aerodynamic coefficients are presented and their significance is discussed.


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Autor(en) Semaan, Richard | Kumar, Pradeep | Burnazzi, Marco | Tissot, Gilles | Cordier, Laurent | Noack, Bernd R.
TitelReduced-order modelling of the flow around a high-lift configuration with unsteady Coanda blowing
HerausgeberJournal of Fluid Mechanics (2016), vol. 800, pp. 72–110. (Reviewed)
Erscheinungsjahr2016
Abstract
We propose a hierarchy of low-dimensional proper orthogonal decomposition (POD) models for the transient and post-transient flow around a high-lift airfoil with unsteady Coanda blowing over the trailing edge. The modal expansion comprises actuation modes as a lifting method for wall actuation following Graham et al. (Intl J. Numer. Meth. Engng, vol. 44 (7), 1999, pp. 945–972) and Kasnako ̆glu et al. (Intl J. Control, vol. 81 (9), 2008, pp. 1475–1492). A novel element is separate actuation modes for different frequencies. The structure of the dynamic model rests on a Galerkin projection using the Navier–Stokes equations, simplifying mean-field considerations, and a stochastic term representing the background turbulence. The model parameters are identified with a data assimilation (4D-Var) method. We propose a model hierarchy from a linear oscillator explaining the suppression of vortex shedding by blowing to a fully nonlinear model resolving unactuated and actuated transients with steady and high-frequency modulation of blowing. The models’ accuracy is assessed through the mode amplitudes and an estimator for the lift coefficient. The robustness of the model is physically justified, and then observed for the training and the validation dataset.


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Autor(en) Lippitz, Nicolas | Maudarbocus, Samir | Rösler, Joachim
TitelThe influence of cold rolling on the pore morphology and flow resistivity of porous aluminum
HerausgeberSixth International Conference on Porous Media and Its Applications in Science, Engineering and Industry, Waikoloa, Hawaii, USA, 2016
Erscheinungsjahr2016
Abstract
Materials with an open porosity are used in many applications, such as filters, acoustic absorbers or heat exchangers. For these applications the pore size and shape as well as the depending flow resistivity are important parameters and need to be adjusted for the specific case. The material parameters are usually defined by the manufacturing process and are therefore signature for different types of porous materials. In this study the porosity, pore shape and the depending flow resistivity of a given material are adjusted using a cold rolling process. The material chosen is a porous aluminum with a porosity of about 50% and relatively large pores, what allows to adjust pore size and porosity on large scale. To characterize the initial porous structure and describe the structural evolution during cold rolling, three dimensional X-ray scans for various degrees of deformation were taken. To analyze pore size and pore shape a line segmentation technique was applied to image stacks extracted from the 3D reconstructions parallel to the three main surfaces of the rolled plate (parallel and perpendicular to the rolled surface). Thus it is possible to examine the formation of an anisotropic porous structure and compare pore shapes and sizes for different degrees of deformation and orientations within the rolled plate. These results are then compared to the evolution of the flow resistivity, which was measured for the three main orientations.
Internet Linkhttp://dc.engconfintl.org/porous_media_vi/6


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Autor(en) Schwerter, Martin | Leester-Schädel, Monika | Dietzel, Andreas
TitelFlip-Chip montierbarer Mikro-Drucksensor zum Einsatz in harscher Umgebung
HerausgeberTagungsband des 4SMARTS Symposiums vom 6. - 7. April 2016 in Darmstadt, Seite 353–359
Erscheinungsjahr2016
Abstract
Im Folgenden wird ein neuartiger, „umgekrempelter“ piezoresistiver Drucksensor vorgestellt. Der Sensorgrundkörper wird statt aus dem sonst üblichen Silizium aus Borofloat-Glas hergestellt; aus ersterem wird dagegen nur eine dünne, funktionale Membran mit den piezoresistiven Elementen gefertigt. Der Herstellungsvorgang erlaubt eine invertierte Anordnung der Siliziummembran, sodass die piezoresistiven Elemente im Sensorinneren liegen und eine Kontaktierung dieser durch das Glas nach unten ermöglicht wird. Der Sensor kann daher mittels Flip-Chip-Technik montiert und verlötet werden. Die Herstellung der Kontaktierungslöcher und der Referenzdruckkammer im Glas sowie die Strukturierung der Bond-Metallschicht erfolgen mittels Femtosekundenlaser-Ablation bei einer Wellenlänger von 1030 nm. Die elektrische Kontaktierung und die metallische Bondschicht resultieren aus derselben Metallisierung. Dieser Aufbau führt zu einer kleinen Grundfläche von nur 3 x 3 mm² und einer Sensorhöhe von 220 μm. Im Gegensatz zu bestehenden Drucksensorsystemen wird eine absolut flache Sensoroberfläche realisiert, die keine elektrischen Elemente oder Anschlusspads beinhaltet. Somit ist der Sensor sowohl an Luft als auch in Wasser einsetzbar, ohne die Strömung selbst zu beeinflussen. Im Anwendungsfeld stehen daher beispielsweise adaptronische Systeme in der Luftfahrt oder die Integration in dünne, flexible Substrate.
Internet Linkdx.doi.org/10.1515/9783110469240-031


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Autor(en) Blinstrub, Jason | Heinze, Wolfgang | Bertsch, Lothar | Simons, Dick | Snellen, Mirjam
TitelSYSTEM NOISE ASSESSMENT OF AN AIRCRAFT WITH COANDA FLAPS
HerausgeberResearch & Education in Aircraft Design, 12.-14. Sep. 2016, Warschau, Polen
Erscheinungsjahr2016
Abstract
An innovative aircraft design of the Collaborative Research Centre (SFB) 880 features a new active high-lift system. This high-lift system is comprised of a droop-nose leading edge device and a Coanda flap as the trailing edge device. It offers very high lift coefficients and thus the ability to operate at airports that have reduced runway lengths, such as regional airports. Consequently, the assessment of aircraft noise is of utmost importance. The overall system noise on the ground is predicted using a parametric aircraft noise prediction tool. Although a parametric noise source model for the Coanda flap does not exist, it is estimated with a conventional Fowler flap model to evaluate the qualitative noise reduction potentials. The new design is compared with a regular aircraft that is equipped with a conventional high-lift system. Both designs are tested on individually calculated continuous decent approaches. The results show that airframe noise of the new aircraft is decreased due to later flap deflection and reduced speed. The engine noise, however, is significantly increased, especially on the glide slope. Hence, it dominates the overall noise on the ground, eliminating the benefits of the airframe noise reduction in the proximity of the airport. It is shown that the noise reduction potentials can only be exploited if the approach trajectory is individually optimized for low-noise.


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Autor(en) Müller, Thomas | Hennings, Holger
TitelRotordynamic Validation of a Twin Rotor-bearing System Considering Gyroscopic Forces and Bearing Dynamics with a Multibody Formulation: Application to a Geared UHBR Gas Turbine
HerausgeberDLRK, Braunschweig
Erscheinungsjahr2016
Abstract
A rotordynamic study for an engine with an ultra-high bypass ratio (BPR=17) was performed using a multibody (Simpack) and a finite element (Ansys) description. The previous validation based on an analytical system of a coaxial counter rotating twin rotor model was performed to legitimize the use of Simpack and the methodological approach, which included the modal reduction of finite element bodies and their integration in the multibody description. Therefore the eigenfrequencies as a function of the rotational speed and the unbalance respond due to eccentricity were compared. The same methodology was then applied to the UHBR engine. Performing an evaluation of the critical speed map, Campbell diagram and an unbalance respond analysis to identify the system behavior. By examining the system respond due to an unbalance force the need of a full modal description of the rotating parts with respect to a suspension point of the complete engine was shown.
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Internet Linkhttp://publikationen.dglr.de/?tx_dglrpublications_pi1[document_id]=420094


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Autor(en) Rossian, Lennart | Faßmann, Benjamin | Ewert, Roland | Delfs, Jan
TitelPrediction of Porous Trailing Edge Noise Reduction Using Acoustic Jump-Conditions at Porous Interfaces
Herausgeber22nd AIAA/CEAS Aeroacoustic Conference, Lyon, 2016
Erscheinungsjahr2016
Abstract
Reduction of noise generated at geometric edges can be achieved by replacing solid material with porous inlays. The acoustic benefit for airfoil trailing edge noise was ex- perimentally found to yield a reduction in sound pressure level of approximately 6 dB. Numerical methods are of interest to and optimal properties of the porosity. A successful method of modeling porous materials is the Volume-Averaging approach. In prior simulations, the prediction of the sound reduction was comparable to measurements over a limited frequency range. This has been enhanced to obtain simulation results which show a better agreement with the experimental findings. At the interface between the free fluid and the porous parts jump conditions are required to model the interaction of the acoustic and flow quantities in these two regimes when it comes to nonhomogeneous materials. This paper presents the perturbation formulation of a set of jump conditions for Computational Aeroacoustics (CAA), already known from Computational Fluid Dynamics (CFD). For the numerical implementation, a high-order compact boundary scheme is derived. Furthermore, the description of complex anisotropic materials is pursued. In a hybrid two-step CAA/CFD procedure, the turbulence statistics from the corresponding solution of the Volume-Averaged Navier-Stokes-Equations (VANS) is used to trigger vortices generating turbulent-boundary-layer trailing-edge noise (TBL-TEN).


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Autor(en) Diekmann, Jobst Henning | Keller, Dennis | Faez, Edris | Rudnik, Ralf | Gollnick, Volker
TitelFLIGHT MECHANICS MODEL FOR SPANWISE LIFT AND ROLLING MOMENT DISTRIBUTIONS OF A SEGMENTED ACTIVE HIGH-LIFT WING
Herausgeber65. Deutscher Luft- und Raumfahrtkongress, Braunschweig
Erscheinungsjahr2016
Abstract
In this study the aerodynamics of wings using an active high-lift system are investigated. The target is the flight mechanical description of the spanwise forces and resulting moments and the influence of the active high-lift system to their distribution. The high-lift system is a blown flap system divided into six segments per wing. Each segment is assumed to be individually controlled, so the system shall be used for aircraft control and system failure management. This work presents a flight mechanical model for fast-time simulation of flight dynamics, which has been derived from high-fidelity CFD results. An assessment of single segment system failures will be presented including recommendations for compensation of either lift or rolling moment loss. For this investigation, the compensation is required to act at the same wing on which the failure appears. Thus, the potential for an increase of system reliability shall be proven. The results show that less performance investment is necessary to compensate the rolling moment of a failing segment instead of its lift. However, large performance increases for the remaining wing segments occur for some of the failure cases.


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Autor(en) Kauth, Felix | Narjes, Gerrit | Müller, Jan | Mertens, Axel | Ponick, Bernd | Seume, Jörg
TitelHighly Integrated Electrically Driven Active High-Lift Compressor Systems for Future Civil Aircraft
HerausgeberGreener Aviation Conference, Brussels, 2016
Erscheinungsjahr2016
Abstract
This paper presents the current status of the develop- ment of an electrically driven high-speed compressor for active high-lift systems (AHLS). A high-speed electrical machine with a high power-to-weight ratio was developed, which utilizes the compressor intake air as a coolant. The power electronics were designed with a new approach to reduce the required space. Furthermore, they are cooled by the intake air flow. Automatic optimization methods were applied to design a single-stage axial compressor that provides the required air flow for the Coanda jet. To obtain high pressure ratios with high efficiency, a new transonic design with a high radial velocity component was chosen.


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Autor(en) Narjes, Gerrit | Müller, Jan | Kauth, Felix | Seume, Jörg | Mertens, Axel | Ponick, Bernd | Müller, Jan
TitelDesign Considerations for an Electrical Machine Propelling a Direct Driven Turbo Compressor for use in Active High-Lift Systems
HerausgeberESARS itec, Toulouse, Frankreich, 2016 (Reviewed)
Erscheinungsjahr2016
Abstract
This paper presents the design approach of a power train used in an advanced high-lift system for future aircraft. Aircraft applications require an ultra-light and integrated design leading to an electrical machine with a high power to weight ratio of 2.82 kW/kg. To achieve additional high lift during take-off and landing, air is blown out at the back flaps of the aircraft wings using a turbo compressor which is directly driven by an inverter-fed electrical machine. The design of the power train and the electrical machine in particular is discussed under different aspects, e.g. the electromagnetic design and the mechanical demands including the selection of a feasible rotor armour. This paper identifies the interfaces between the different factors and describes their dependencies.


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Autor(en) Blech, Christopher | Falkenberg, Paul | Langer, Sabine Christine | Vietor, Thomas
TitelA geometrical approach to remove stress singularities in continuum models of multi-material structures
HerausgeberProc. Appl. Math. Mech., DOI 10.1002/pamm.201510130, 15, Wiley-VCH Verlag GmbH, 279 – 280, GAMM, Lecce, Italy, 2015
Erscheinungsjahr2015
Abstract
In the frame of stress based topology optimisation multi-material structures are investigated. At the interface of dissimilar materials an adhesive joint shall be considered. Selecting a continuum approach to model the two adherends and the adhesive, stress singularities occur at the material-interfaces due to the difference in the impedance [1]. This contribution investigates a geometrical opportunity to remove singularities at the interface of two different linear elastic structures. Sensitivities of important parameters are qualitatively shown by a simple example consisting of two cubes under tension.


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Autor(en) Unruh, Oliver | Blech, Christopher | Monner, Hans Peter
TitelNumerical and Experimental Study of Sound Power Reduction Performance of Acoustic Black Holes in Rectangular Plates
HerausgeberSAE Int. J. Passeng. Cars - Mech. Syst., doi:10.4271/2015-01-2270, 8(3), SAE International, SAE, Detroit, Michigan, USA, 2015
Erscheinungsjahr2015
Abstract
Global attenuation of structural velocities is one of the most effective approaches in order to reduce noise emitted by shell structures such as a car roof or aircraft fuselage panels. This global reduction can be achieved by the application of passive damping treatments like constraint layer damping on large fractions of the vibrating surface. The main disadvantage of this approach arises from the fact that it leads to increasing total cost and weight of the structure. To overcome this problem, acoustic black holes can be used to create locations with high vibration amplitudes and low bending waves velocity in order to dissipate the energy of structure borne sound by very limited application of damping treatments. Acoustic black holes are funnel shaped thickness reductions that attract sound radiating bending waves and allow a global vibration reduction by an acceptable use of additional damping. This paper presents the results of a numerical and experimental study of acoustic black holes located on a rectangular plate. The presented work is focused on the influence of size, position and number of acoustic black holes on the acoustic performance. A large number of different configurations of these parameters is studied by finite-element-analysis and evaluated in terms of vibration amplitude and sound power level. In order to confirm simulation results the most efficient configuration is implemented in laboratory setup and characterized in terms of vibrational and acoustic performance.


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Autor(en) Schwerter, Martin | Hecht, Lars | Koch, Eugen V. | Leester-Schädel, Monika | Büttgenbach, Stephanus | Dietzel, Andreas
TitelLiquid polyimide as a substrate for aeronautical sensor systems
HerausgeberSPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring, San Diego, 2015
Erscheinungsjahr2015
Abstract
Using more and more controlled systems in future aircraft the need of flexible sensors to be applied on curved aircraft structures increases. An appropriate substrate material for such flexible sensors is polyimide, which is available both as ready-made foil and as liquid polyimide to be spun-on. Latest results in producing and processing of polyimide layers with a thickness of down to 1 μm including designs for thin foil sensors are presented respectively. The successful processing of liquid polyimide is outlined first including the spin-on procedure, soft bake and curing for polymerization. Parameters for spin-on volume and rotation speed on glass substrates along with a comparison with ordinary polyimide foil are presented. High-precision structuring of the polyimide layer is performed either by etching (wet-etching as well as dry etching in a barrel etcher) or ablative removal using a femtosecond laser. In combination with a layer of silicon nitride as an inorganic diffusion barrier a reliable protection for water tunnel experiments can be realized. The fabrication of a protection layer and test results in water with protected sensors are presented. The design of a hot-film anemometric sensor array made on spin-on polyimide is demonstrated. With a thickness of down to 7 μm the sensors can be applied on the surface of wind tunnel models and water tunnel models without impacting the flow substantially. Additionally both the concept and recent results of a silicon sensor integrated in a polyimide foil substrate that can measure pressure as a complementary measurand for aeronautics are illustrated.
Internet Linkhttp://spie.org/Publications/Proceedings/Paper/10.1117/12.2084028


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Autor(en) Lippitz, Nicolas | Rösler, Joachim
TitelDamage Behavior of Sintered Fiber Felts
HerausgeberMetals, ISSN 2075-4701, 5, MDPI AG, 591-602, Basel, Switzerland, 2015 (Reviewed)
Erscheinungsjahr2015
Abstract
The reduction of aircraft noise is important due to a rising number of flights and the growth of urban centers close to airports. During landing, a significant part of the noise is generated by flow around the airframe. To reduce that noise porous trailing edges are investigated. Ideally, the porous materials should to be structural materials as well. Therefore, the mechanical properties and damage behavior are of major interest. The aim of this study is to show the change of structure and the damage behavior of sintered fiber felts, which are promising materials for porous trailing edges, under tensile loading using a combination of tensile tests and three dimensional computed tomography scans. By stopping the tensile test after a defined stress or strain and scanning the sample, it is possible to correlate structural changes and the development of damage to certain features in the stress-strain curve and follow the damage process with a high spatial resolution. Finally, the correlation between material structure and mechanical behavior is demonstrated.
Internet Linkhttp://www.mdpi.com/2075-4701/5/2/591/pdf


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Autor(en) Semaan, Richard | Kumar, Pradeep | Burnazzi, Marco | Tissot, Gilles | Cordier, Laurent | Noack, Bernd R. | Vorreiter, Arne | Friedrichs, Jens | Delfs, Jan
TitelReduced-order modeling of the flow around a high-lift configuration with unsteady Coanda blowing
HerausgeberJournal of Fluid Mechanics (Reviewed)
Erscheinungsjahr2015
Abstract
We propose a low-dimensional POD model for the transient and post-transient flow around a high-lift airfoil with unsteady Coanda blowing over the trailing edge. This model comprises the effect of high-frequency modulated blowing which mitigates vortex shedding and increases lift. The structure of the dynamical system is derived from the Navier-Stokes equations with a Galerkin projection and from subsequent dynamic simplifications. The system parameters are determined with a data assimilation (4D-Var) method. The boundary actuation is incorporated into the model with actuation modes following Graham et al. 1999 and Kasnakoglu 2008. As novel enabler, we show that the performance of the POD model significantly benefits from employing additional actuation modes for different frequency components associated with the same actuation input. In addition, linear, weakly nonlinear and fully nonlinear models are considered. Already the weakly nonlinear system is found to describe unactuated and actuated flow transients well, emphasizing that the actuated base-flow change is key in mitigating vortex shedding. As expected, the linear system exhibits significant drawbacks, whereas the consideration of all quadratic modal interactions improves the resolution. The current study suggests that separate actuation modes for different actuation frequencies improve Galerkin model performance, in particular with respect to the important base-flow changes.


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Autor(en) Krukow, Ian | Neuert, Nora | Dinkler, Dieter
TitelDynamic instabilities of circulation controlled aerofoils
HerausgeberIFASD 2015, St. Petersburg, Russland
Erscheinungsjahr2015
Abstract
The continuously rising volume of air traffic demands for a correspondingly rising capacity of airports. One possible scenario is the extended use of small, existing airports for point-to-point connections. However, in order to use the shorter runways, the high-lift systems have to be improved significantly. This can be achieved by active circulation control making use of the Coand˘a effect. Though subject to research for several decades, there are still a number of issues to consider in order to make it work for a commercial aircraft. Investigating the aeroelastic behaviour is essential for stability issues. It turns out that the application of active circulation control leads to two additional flutter phenomena, which do not occur with conventional aircraft. Both of them are single degree of freedom flutter – related to heave and pitch motion, respectively – occurring at low velocities as in landing approach.


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Autor(en) Atalayer, Caglar | Friedrichs, Jens | Wulff, Detlev
TitelS-Duct Intake Configuration Sensitivity of a Highly Loaded Turboprop by CFD Methods
HerausgeberProceedings of ASME Turbo Expo 2015: Turbine Technical Conference and Exposition, Montreal, Canada (Reviewed)
Erscheinungsjahr2015
Abstract
Highly-loaded turboprop intake was investigated for two different shaft connection types to assess the configuration sensitivity on performance. Turboprop intakes inherently have S-shape to bend around the gearbox, which have significant effects on the flow. Previous geometric sensitivity analysis on uninstalled, isolated single scoop S-ducts with shaft penetration showed higher recovery and lower distortion trends for long intakes with shorter ducts. The major pressure loss was observed over the bore due to the penetrating shaft. It is expected that changing the configuration to wrap-around will overcome the loss introduced by flow around the bore. The two configurations were compared by varying the S-duct curvatures using computational methods. The results showed an increase in recovery with lower total pressure distortion levels for wrap-around configuration of the same sizes. The gain in the recovery by the configuration change was observed to be similar to the gain when the ducts were shortened. However, wrap-around S-duct suffered from higher swirl distortion than shaft penetration of the same size but these were observed to be lower than the shaft penetration type with short ducts. Distortion intensities showed opposite trends for the two configurations, with wrap-around producing low distortion in circumferential whereas high in radial direction. The results will be used as the basis for the turboprop intake design and its over-the-wing integration on the high-lift aircraft.
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Autor(en) Schmitz, Andre | Horst, Peter
TitelDEVELOPMENT AND INVESTIGATION OF A HYBRID CURVATURE-MORPHING SKIN STRUCTURE
Herausgeber20th International Conference on Composite Materials, Copenhagen, 19-24th July
Erscheinungsjahr2015
Abstract
A short introduction on curvature-morphing skins is given. The studied structure consists of outer hybrid layers (highly strained in operation due to large curvature alterations) with unidirectional discrete composite bundles embedded in an ethylene-propylene-diene rubber foundation. Within the morphing context, the presented work focusses on the crucial aspect of compressive strength along these bundles. However, large compressive strength is achieved if buckling of the bundles can be avoided. To characterize the buckling behaviour, samples are manufactured and tested in an appropriate set-up under almost real boundary conditions (avoidance of continuous anti-buckling guides). Results are compared to the outcome of numerical linear eigenvalue analyses.


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Autor(en) Teichel, Sönke | Verstraete, Tom | Seume, Jörg
TitelOptimized Multidisciplinary Design of a Small Transonic Compressor for Active High-Lift Systems
HerausgeberProceedings of International Gas Turbine Congress, Tokyo (Reviewed)
Erscheinungsjahr2015
Abstract
This paper presents the methodology and results of the optimized, multidisciplinary design of a small, single stage, axial compressor with a corrected mass-flow rate of about 1.11 kg/s and a total pressure ratio of up to 2.57 at the design point. The compressor is part of an electrically powered active high lift system (AHLS) for future civil aircraft. An automated process using numerical models to evaluate aerodynamic performances and mechanical loads due to centrifugal forces is used for the design. This valuation process is coupled to an evolutionary algorithm to help investigate the designspace. A parameterization strategy was developed to cover a wide design-space, excluding unreasonable designs. The goal was to satisfy the design requirements high pressure ratio, high power density and limited rotation speed imposed by the application of the AHLS. The resulting design of a highly loaded single stage axial compressor covers the operating points of the AHLS at efficiencies higher than 85%for lower mass-flow rates, while at higher mass-flow rates it drops to 80 %.


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Autor(en) Schmitz, Andre | Horst, Peter
TitelNumerical modelling of the change in stiffness properties of cross-ply laminates subjected to large bending curvatures
HerausgeberKey Engineering Materials, 978-3-03785-830-1, 577-578, Trans Tech Publications, 173-176 (Reviewed)
Erscheinungsjahr2014
Abstract
This paper presents a 3D unit-cell approach which enables the estimation of bending, inplane and coupling stiffness properties in the sense of the classical laminated plate theory for arbitrarily heterogeneous plates. Periodic boundary conditions which simultaneously allow for in-plane as well as for bending and twist deformation modes are introduced. Additionally, bending experiments of glass-fibre/epoxy cross-ply laminates with cracked outer layer at the tension side are conducted and the stiffness degradation due to these transverse cracks is compared to numerical results.
Internet Linkhttp://www.scientific.net/KEM.577-578.173


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Autor(en) Schmitz, Andre | Horst, Peter
TitelBending deformation limits of corrugated unidirectionally reinforced composites
HerausgeberComposite Structures, ISSN: 0263-8223, 107, Elsevier Ltd., 103–111 (Reviewed)
Erscheinungsjahr2014
Abstract
This paper concerns about deformation limits of circular corrugated unidirectional reinforced composites for bending dominated applications. Hence, a two-dimensional analytical stress function approach is used which takes through-thickness normal stresses into account. Hereby, the possible failure modes, namely fibre fracture and layer delamination, of unidirectional laminated circular corrugated sheets are predicted. Additionally, the accurate representative bending stiffness in corrugated-direction is extracted by using an energy approach. The influence of corrugation geometric parameters on deformation limits and stiffness is experimentally as well as theoretically investigated. For this reason, large curvature validation experiments of four different corrugation types are conducted by means of a specially constructed bending device. Finally, bending charts are provided facilitating the choice of an appropriate corrugation geometry during a preliminary design phase.
Internet Linkhttp://dx.doi.org/10.1016/j.compstruct.2013.07.048


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Autor(en) Sommerwerk, Kay | Haupt, Matthias
TitelDesign analysis and sizing of a circulation controlledCFRP wing with Coanda flaps via CFD-CSMcoupling
HerausgeberCEAS Aeronautical Journal, Vol. 5, No. 1, 2014, pp 95-108 (Reviewed)
Erscheinungsjahr2014
Abstract
Preliminary design tools are essential during aircraft design to make conclusions about an aircraft's performance. Generally this process employs methods of low and medium fidelity to create comparatively fast results for a high number of parameter variations. High fidelity methods are needed to verify theses results and to consider components in more detail. A 100 PAX commercial aircraft with short take-off and landing capabilities of 800 meters with circulation controlled high lift devices is under investigation at the Collaborative Research Centre SFB 880. In this paper, a global wing analysis with a high detail model is conducted and the results are compared with results attained with a preliminary aircraft design tool. Several detailed designs for the air feed system integration are proposed and examined regarding weight and stiffness characteristics on a representative high lift device section model. Fluid-structure coupling is employed during all analyses to transfer aerodynamic loads and structural displacements. The aeroelastic impact of the slot stiffness on the Coanda effect during landing is then quantified. The attained aerodynamic performance results and structural characteristics of each configuration are compared and the advantages are discussed.
Internet Linkhttp://dx.doi.org/10.1007/s13272-013-0093-9


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Autor(en) Radespiel, Rolf | Heinze, Wolfgang
TitelSFB 880 - fundamentals of high-lift for future commercial aircraft
HerausgeberCEAS Aeronautical Journal, DOI 10.1007/s13272-014-0103-6 (Reviewed)
Erscheinungsjahr2014
Abstract
The recently founded Collaborative Research Centre SFB 880 of the Technische Universität Braunschweig, „Fundamentals of High-Lift for Future Commercial Aircraft“, develops new knowledge in aircraft noise, in advanced approaches towards active high lift, and in the dynamics of flight with active high lift during short take-off and landing operations. The Research Centre has therefore devised a range of research projects that aim at integrated aeroacoustic and aerodynamic design capabilities for drastic noise reductions and at the generation of active high lift with an extremely high efficiency of the used onboard power. Flight dynamics of commercial aircraft with increased lift capabilities for take-off and landing due to active control means and including the effects of aeroelasticity and engine failure modes are also investigated. The Research Centre has developed a joint strategy for technology assessment using high-quality conceptual design data of a reference aircraft that represents the state of the art in CO2 reductions, low noise, and short take-off and landing for point-to-point air connections within Europe. The paper describes the overall strategy of the coordinated research work and gives examples of recent results.
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Internet LinkThe final publication is available at Springer via http://dx.doi.org/10.1007/s13272-014-0103-6


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Autor(en) Schwerter, Martin | Beutel, Tobias | Leester-Schädel, Monika | Büttgenbach, Stephanus | Dietzel, Andreas
TitelFlexible hot-film anemometer arrays on curved structures for active flow control on airplane wings
Herausgeber Microsystem Technologies Special Issue: Smart Sensors, Actuators and MEMS 2013, ISSN: 0946-7076, Springer, 2014 (Reviewed)
Erscheinungsjahr2014
Abstract
A set of flexible MEMS sensor arrays for flow measurements in boundary layers is presented. The sensor principle of these anemometers is based on convective heat transfer from a hot-film into the fluid. Each sensor consists of a nickel sensing element between copper supply tracks. The functional layers are attached either on a ready-made polyimide foil or on a spin-on polyimide layer. These variants are designed to meet the requirements of measurements in different environments. Spin-on technology enables the use of very thin polyimide layers, ideally suited for measurements in transient flows. It is a unique characteristic of the presented arrays that their total thickness can be scaled from 7 to 52 μm. This is essential, because the sensor thickness has to be adapted to the varying thickness of the boundary layers in different aerodynamic tests. With these sensors we meet the special requirements of a wide range of fluid mechanic experiments but in particular those of future active flow control on airplane wings. For less critical flow conditions with much thicker boundary layers, thicker sensors might be sufficient and cheaper, so that sensors fabricated on ready-made foils are perfect for these applications. Since the presented sensors are flexible, they can be attached on curved aerodynamic structures without any geometric mismatches. The entire development, starting from theoretical investigations, is described. Further, the micro-fabrication is discussed, including photolithography, sputtering and wet-etching. In particular the wet-etching of the sensing element is found to be critical for the functional characteristics.
Internet Linkhttp://link.springer.com/article/10.1007/s00542-013-2054-y


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Autor(en) Krukow, Ian | Dinkler, Dieter
TitelA Reduced-Order Model for the Investigation of the Aeroelasticity of Circulation Controlled Wings
HerausgeberCEAS Aeronautical Journal (2014) 5:145-156 (Reviewed)
Erscheinungsjahr2014
Abstract
The application of active circulation control allows shortening of runways which can be significant in particular cases. The goal of the present paper is to study the influence of the circulation control on the aeroelastic behaviour of wings. For numerical analyses a simplified computational model is presented, which allows for systematic parameter variations. The model is based on model reduction using modal analysis, so that an efficient performance of numerical studies is possible as well as the integration of the aeroelasticity into a flight dynamics model.
Internet Linkhttp://www.springer.com/alert/urltracking.do?id=L483de8fMf1751eSb0d5fd1


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Autor(en)Keller, Dennis
TitelNumerical Approach Aspects for the Investigation of the Longitudinal Static Stability of a Transport Aircraft with Circulation Control
HerausgeberNew Results in Numerical and Experimental Fluid Mechanics IX, 4629 (Reviewed)
Erscheinungsjahr2014
Abstract
The aim of the investigation is to gain more certainty about the approach to evaluate the longitudinal stability and controllability of a high-lift configuration of a transport aircraft with circulation control. Since the work was carried out with a CFD RANS approach, a comprehensive meshing study was performed in advance.


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Autor(en) El Sayed M, Yosef | Semaan, Richard
TitelProgress toward Closed Loop Control of a Flow around an Airfoil with Coanda Blowing
HerausgeberSpringer, ICOMASeF, Prato (Tuscany) Italy, 2014
Erscheinungsjahr2014
Abstract
Progress toward developing a closed loop control of flow around an airfoil with a Coanda flap is presented. Two loop components were addressed and analysed for the reference no-blowing case: the estimator and its input signal. For the estimator, a Proper Orthogonal Decomposition (POD) Galerkin model based on unsteady Reynolds averaged Navier-Stocks (uRANS) data was evaluated. To compensate for the unresolved dissipative scales in uRANS and for truncation error, the POD Galerkin model was calibrated by introducing an eddy viscosity term. The cali-brated POD Galerkin model succeeded in replicating the time coefficients of the first two modes but failed to replicate the higher modes. The sensor location over the flap was optimized using modified Linear Stochastic Estimation (mLSE). With an optimal sensor placement it was possible to determine the state of the flow more accurately than for the same number of evenly spaced sensors.


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Autor(en) Rösler, Joachim | Björn Hinze, Waldemar Krause
TitelA Concept for the Control of Pore Size in Superalloy Membranes
HerausgeberMetals, ISSN 2075-4701, 4, MDPI AG, 1-7, Basel, Switzerland, 2014 (Reviewed)
Erscheinungsjahr2014
Abstract
A new method to adjust the pore size in superalloy membranes is shown, utilizing controlled cooling from solution heat treatment of the solid superalloy. Hereby, the nucleation rate and, thus, the size of the γ'-precipitates can be varied to a large extent. This leads to a corresponding variation in the pore size once the membrane material is produced by directional coarsening of the γ'-phase to an interconnected network and subsequent selective extraction of the γ-phase. Furthermore, it was found that coherent and incoherent γ'-precipitates can be used alike to fabricate superalloy membranes, and yet, result in vastly different pore morphologies. The findings widen the application range of this novel material class.
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Internet Linkhttp://www.mdpi.com/2075-4701/4/1/1/pdf


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Autor(en) Beck, Silja | Langer, Sabine
TitelFlow-Induced sound of structures with porous layer (title in publication changed to: Modeling of flow-induced sound in porous materials)
HerausgeberInt. J. Numer. Meth. Engng 2014; 98:44–58 (Reviewed)
Erscheinungsjahr2014
Abstract
The impact of flow on a structure plays a crucial part when considering structural behavior, for example, in aviation. As structural vibrations (also denominated as structural sound) propagate within a structure, sound radiation is a likely consequence. To reduce the emission of noise, the use of poroelastic material is investigated. The approach consists in applying a poroelastic layer on the surface submitted to flow, as such utilizing the damping properties of poroelastic material. To predict flow-induced sound, a computational model has been developed to account for (1) flow-induced sound immission into a structure; (2) sound propagation; and (3) possible resulting sound radiation. Con- sistent formulation of the interactions between the components—that is, flow, poroelastic material, elastic structure, and acoustic fluid—allows to apply different simulation techniques for each component and thus to exploit each method’s advantages. The key aspect of this work is the formulation of the interface con- ditions to couple flow with poroelastic material. The proposed and implemented coupling conditions are studied. The given example shows a possible application and demonstrates the effectiveness of poroelastic material to reduce flow-induced sound emission.
Internet Linkhttp://onlinelibrary.wiley.com/doi/10.1002/nme.4622/abstract


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Autor(en) Schmitz, Andre | Horst, Peter
TitelA new curvature morphing skin: manufacturing, experimental and numerical investigations
Herausgeber16th European Conference on Composite Materials, Seville, Spain, 2014
Erscheinungsjahr2014
Abstract
Currently, the aerospace sector tries to bring morphing technology into application in order to improve flight performance, reduce noise and extend the operational envelope. This work presents a new curvature morphing skin which is intended to be applicable at a highly contourvariable airliner’s droop nose. The key characteristic of such skin is a large curvature at rupture in droop-direction while simultaneously providing a high perpendicular sti ness. Hence, two manufacturing processes for a hybrid composite-elastomer skin have been developed. After introducing the structural concept with the appropriate manufacturing processes, large bending experiments are presented. Finally, in order to gain further understanding, some numerical investigations are performed by using a finite element unit-cell.


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Autor(en) Schmitz, Andre | Horst, Peter
TitelA finite element unit-cell method for homogenised mechanical properties of heterogeneous plates
HerausgeberComposites Part A, ISSN: 1359-835X, 61, Elsevier Ltd., 23-32 (Reviewed)
Erscheinungsjahr2014
Abstract
This paper presents a 3D unit-cell approach which enables estimations of all bending, in-plane and coupling properties in the sense of the classical laminated plate theory for heterogeneous plates. For this reason, periodic boundary conditions which simultaneously allow in-plane as well as bending/twisting deformation modes are introduced. In contrast to existing approaches, the 3D unit-cell is connected with the macroscopic plate theory by means of prescribed loads and the extraction of strains/curvatures. Novel bending experiments at large curvatures of E-glass-fibre/epoxy cross-ply laminate with cracking outer ply at the bending tension side are conducted. Subsequently, numerical results are validated by comparing them to the measured bending stiffness degradation. Further, the effects of the single-sided transverse cracks on relevant stiffness properties are computed.
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Internet Linkhttp://www.sciencedirect.com/science/article/pii/S1359835X14000281


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Autor(en) Rudenko, Anton | Monner, Hans Peter | Rose, Michael
TitelA Process Chain for Structural Optimization of a Smart Droop Nose for an Active Blown High Lift System
Herausgeber22ND AIAA/ASME/AHS ADAPTIVE STRUCTURES CONFERENCE / US Washington DC 2014
Erscheinungsjahr2014
Abstract
A detailed analysis of today’s commercial aircraft determines an increased demand for high lift systems that cannot be provided by prevailing evolutionary technology development. This especially applies to the topics of noise reduction and performance increase for start and landing. An active blown Coandă-flap based high lift system, which is investigated within the German national Collaborative Research Centre 880, would be an alternative to today’s slats and flaps and promises to contribute to those goals. An adaptive gapless droop nose with an exceedingly high grade of leading edge morphing is proven to be a key part of such a system, and thus a structural optimization framework for this technology is developed by the DLR. The content of this paper is formed by the detailed presentation of the framework for optimization of a composite skin combined with an actuation kinematics.
Internet Linkhttp://arc.aiaa.org/doi/pdf/10.2514/6.2014-1414


Die folgende Veröffentlichung ist nur INTERN sichtbar!

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Autor(en) Teichel, Sönke | Verstraete, Tom | Seume, Jörg
TitelOptimized Axial Compressor Design using an Evolutionary Algorithm and TRACE
HerausgeberTRACE User Conference 2014, Cologne, Germany
Erscheinungsjahr2014
Abstract
The process of designing turbomachinery combines the fields of aero design and structural design. Interactions with load and operating conditions define the boundary conditions in a complex way and need to be considered. Automated, multi-objective design optimization is a powerful method to investigate a wide range of design parameters in order to find an optimum design with respect to counteracting objectives. For the design task of a compact and highly loaded single stage compressor, an optimized design process chain was built. This design chain uses the optimization environment CADO developed by the von Karman Institute, Belgium and the structural finite element program CalculiX. For automated aerodynamic evaluation, TRACE is coupled with the optimization process. The geometry data given by the optimizer’s geometry generation tool is transformed in order to match the requirements of the G3DHexa tool. Much care was taken to develop a robust computational setup in TRACE to reliably solve the flow field of the many different variations of the compact, single stage, transonic axial compressor in the automated optimization process. The presentation gives insight into the strategy and solutions found to solve the challenges during the process of developing this tool chain. A brief overview of the results of the optimization will be given.


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Autor(en) Chahine, Christopher | Seume, Jörg | Verstraete, Tom
TitelTHE INFLUENCE OF METAMODELING TECHNIQUES ON THE MULTIDISCIPLINARY DESIGN OPTIMIZATION OF A RADIAL COMPRESSOR IMPELLER
HerausgeberProceedings of ASME Turbo Expo 2012, Proceedings of ASME Turbo Expo 2012 (Reviewed)
Erscheinungsjahr2014
Abstract
Aerodynamic turbomachinery component design is a very complex task. Although modern CFD solvers allow for a detailed investigation of the flow, the interaction of design changes and the three dimensional flow field are highly complex and difficult to understand. Thus, very often a trial and error approach is applied and a design heavily relies on the experience of the designer and empirical correlations. Moreover, the simultaneous satisfaction of aerodynamic and mechanical requirements leads very often to tedious iterations between the different disciplines. Modern optimization algorithms can support the designer in finding high performing designs. However, many optimization methods require performance evaluations of a large number of different geometries. In the context of turbomachinery design, this often involves computationally expensive Computational Fluid Dynamics and Computational Structural Mechanics calculations. Thus, in order to reduce the total computational time, optimization algorithms are often coupled with approximation techniques often referred to as metamodels in the literature. Metamodels approximate the performance of a design at a very low computational cost and thus allow a time efficient automatic optimization. However, from the experiences gained in past optimizations it can be deduced that metamodel predictions are often not reliable and can even result in designs which are violating the imposed constraints. In the present work, the impact of the inaccuracy of a metamodel on the design optimization of a radial compressor impeller is investigated and it is shown if an optimization without the usage of a metamodel delivers better results. A multidisciplinary, multiobjective optimization system based on a Differential Evolution algorithm is applied which was developed at the von Karman Institute for Fluid Dynamics. The results show that the metamodel can be used efficiently to explore the design space at a low computational cost and to guide the search towards a global optimum. However, better performing designs can be found when excluding the metamodel from the optimization. Though, completely avoiding the metamodel results in a very high computational cost. Based on the obtained results in present work, a method is proposed which combines the advantages of both approaches, by first using the metamodel as a rapid exploration tool and then switching to the accurate optimization without metamodel for further exploitation of the design space.


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Autor(en) Mößner, Michael | Radespiel, Rolf
TitelImplementation of Flow through Porous Media into a Compressible Flow Solver
HerausgeberNew Results in Numerical and Experimental Fluid Mechanics IX, ISBN 978-3-319-03157-6, Volume 124 , Springer International Publishing, page 465-473 (Reviewed)
Erscheinungsjahr2014
Abstract
A method for simulating turbulent compressible flow through porous material is presented. The demonstration is based on spatial and time averaging of the Navier-Stokes equations. The averaging procedure leads to additional terms which have to be modelled. The integration of the resulting theory into the flow solver DLR TAU is explained. The extended code is verified by analytical solutions which are used as reference.
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Autor(en) Beck, Silja | Uphoff, Sonja | Langer, Sabine | Krafczyk, Manfred
TitelSensitivity of the slip rate coefficient in fluid flow – poroelastic coupling conditions
HerausgeberProceedings in Applied Mathematics and Mechanics, 85th Annual Meeting of the International Association of Applied Mathematics and Mechanics, Erlangen
Erscheinungsjahr2014
Abstract
To model flow-induced structural vibrations, an interface to couple fluid flow and poroelastic material in a finite element formulation has been developed. One parameter of this interface condition is the slip rate coefficient, resulting from the so- called Beavers-Joseph-Saffman condition. This condition states that the jump in tangential velocity at a fluid flow – porous interface is proportional to the shear stress. Up to now no a priori determination of this parameter exists, and the known parameter range has been deducted from measurements, i. e., in our case from the results of the pore-resolving simulations. When modeling realistic problems assuming incompressible fluids, vectorial flow velocity and scalar pressure interact with the poroelastic material. As the slip rate coefficient only influences the tangential contributions, its overall influence is not clear. In this work, the sensitivity of the slip rate coefficient regarding the interface’s coupling conditions is evaluated.


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Autor(en) Rurkowska, Katherina | Beck, Silja | Langer, Sabine
TitelInfluence of porous materials on structure-borne sound in aircraft application
HerausgeberProceedings of DAGA 2014, Deutsche Gesellschaft für Akustik e. V. (DEGA)
Erscheinungsjahr2014
Abstract
Porous surfaces are used to influence the flow noise and the excitation of the structure-borne noise. Within the project Sonderforschungsbereich 880 Fundamentals of High Lift for Future Civil Aircraft, the aim is to reduce sound produced by aircraft propeller drives and trailing edges. The influence of porous layer on the surface of airfoil is evaluated, specifically on the upper surface of a channel wing. A sensitivity analysis is carried out in or- der to study the behaviour of the structure-borne sound with the implementation of porous material layers. Mi- croperforated plates, sintered fibre felts and metal foam materials are considered. To perform this study a simple structure representing an airfoil segment is used. Some results showing the influence of a porous layer applied on a generic channel wing geometry are presented as well.


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Autor(en) Kumar, Pradeep | El Sayed, Yosef | Semaan, Richard
TitelOptimized sensor placement over a 2D airfoil with Coanda blowing for flow control applications
Herausgeber7th AIAA Flow Control Conference, Atlanta, June 2014
Erscheinungsjahr2014
Abstract
This study investigates the optimal placement of sensors mounted over the flap of a two-dimensional (2D) airfoil equipped with Coanda jet circulation control for the purpose of flow control. The analysis is based on flow field data obtained from 2D unsteady Reynolds averaged Navier-Stokes (uRANS) simulations of a high-lift airfoil with different jet blowing intensities and actuation frequencies, characterizing different flow separation states. Linear stochastic estimation of the proper orthogonal decomposition (POD) is used to estimate the time-coefficients. The optimal sensor locations for any number of sensors configuration are then determined by minimizing the root mean squared error between the determined and the estimated time-coefficients. The results are compared for two types of sensor inputs: pressure sensors and skin-friction sensors. The results show that it is possible to determine the state of flow more accurately using fewer pressure sensors placed at optimized locations than from using the same number of skin friction sensors.


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Autor(en) Atalayer, Caglar | Friedrichs, Jens | Wulff, Detlev
TitelSensitivity Analysis of a Highly Loaded Turboprop S-Duct Intake by CFD Methods
Herausgeber50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Cleveland, Ohio, USA, 2014
Erscheinungsjahr2014
Abstract
S-duct intake of a high power turboprop with unconventional integration types requires additional design objectives rather than a basic sizing, considering the propeller-wing-nacelle interaction effects. Before the conceptual integration process, sensitivity analysis based on the intake performance has been done to identify the limitations on the S-duct geometry using computational methods. The flow simulations were done on an isolated, uninstalled S-duct intake, excluding propeller effects and particle separator, for an initial specification in advance of the actual sizing. The effects of fundamental geometric features, as the intake aspect ratio, duct lengths and spread angle, were investigated on the flow quality through the aerodynamic interface plane (AIP), quantified by total pressure recovery and distortion. The results show a preference to longer S-ducts whereas the shorter inner ducts are observed to be advantegous for their higher recovery capacities with lower distortion levels.
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Autor(en) Uphoff, Sonja | Krafczyk, Manfred | Rurkowska, Katherina | Langer, Sabine | Lippitz, Nicolas | Faßmann, Benjamin
TitelA hierarchical approach to determine acoustic absorption properties of porous media combining pore-resolved and macroscopic models
HerausgeberJournal of Porous Media
Erscheinungsjahr2014
Abstract
Acoustic properties of porous media are very important for numerous industrial applications, the typical goal being to maximize broad band absorption to decrease the sound pressure level of the engineering system under consideration. Up to now acoustic absorption for porous media with complex inner geometry is determined experimentally, as acoustic simulations on the pore scale are computationally challenging due to the tedious geometric reconstruction of computer tomography (CT) data and the corresponding mesh generation as well as substantial computational requirements for the corresponding transient 3D-solvers. The Lattice Boltzmann method (LBM), which is an established computational approach to simulate pore resolved porous media transport problems, has been used successfully for aero-acoustic setups and is utilized in this work to fill this gap. This paper presents a comparison of different experimental and numerical approaches to determine the acoustic absorption of different porous media. Experimental work with an impedance tube was carried out for comparison and CT scans were conducted to supply the detailed numerical simulation with geometry-data of the porous samples. Results of LB simulations for the acoustic impedance of a micro-perforated plate and a felt are shown. Finally we demonstrate how microscopic parameters determined by a pore scale approach can be used to feed homogenized models to bridge the gap towards simulations of components where acoustic absorbers are applied to e.g. wing flaps of airplanes.


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Autor(en) Bertsch, Lothar | Heinze, Wolfgang | Lummer, Markus
TitelApplication of an Aircraft Design-To-Noise Simulation Process
HerausgeberAIAA AVIATION 2014, Atlanta, Georgia, USA
Erscheinungsjahr2014
Abstract
System noise has been integrated as an additional design objective within conceptual aircraft design. The DLR system noise prediction tool PANAM accounts for individual noise sources depending on their geometry and operating conditions. PANAM is integrated into the existing aircraft design framework PrADO from the Technical University of Braunschweig in order to realize a design-to-noise simulation process. In addition, a ray-tracing tool from DLR, SHADOW, is incorporated into the simulation framework in order to account for structural engine noise shielding. The overall simulation process is then applied to identify promising low-noise aircraft concepts. The presented application aims at fan noise reduction through shielding. For the selected reference aircraft, the fan is a major noise source during both landing and takeoff. It is demonstrated, that the aircraft designers influence on the environmental vehicle characteristics is significant at the conceptual design phase. Usually, a trade-off between extensive engine noise shielding and economical flight performance is inevitable. The new design-to-noise process is well suitable to assess all four measures of ICAOs balanced approach.


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Autor(en) Semaan, Richard | El Sayed, Yosef | Sattler, Stephan | Sultana, Kaniz | Burnazzi, Marco | Scholz, Peter | Radespiel, Rolf
TitelA Generalized Reduced-Order Model of Flow around an Airfoil with Circulation Control
HerausgeberAIAA-2014-2517, 7th AIAA Flow Control Conference, 16-20 June, 2014, Atlanta, GA
Erscheinungsjahr2014
Abstract
A low-dimensional generalized model is proposed for a flow around an airfoil with circulation control, describing natural vortex shedding and steady actuation. The suggested application range of the model extends from the un-actuated natural state to the strongly actuated near-steady state. The form of the dynamical system has been based on generalized mean-field consideration. Time resolved PIV snapshots are employed to derive the POD time coefficients and to calibrate the system parameters. The model is solely dependent on the actuation blowing momentum coefficient, and makes a good candidate for flow control applications.


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Autor(en) Müller, Lars | Heinze, Wolfgang | Kozulovic, Dragan | Hepperle, Martin | Radespiel, Rolf
TitelAerodynamic Installation Effects of an Over-the-Wing Propeller on a High-Lift Configuration
HerausgeberJ. Aircraft, Vol. 51, No. 1, pp. 249-258, 2014 (Reviewed)
Erscheinungsjahr2014
Abstract
Preliminary design studies indicate that a cruise-efficient short takeoff and landing aircraft has enhanced takeoff performance at competitive direct operating costs when using high-speed propellers in combination with internally blown flaps. The original tractor configuration is compared to an over-the-wing propeller, which allows for noise shielding. An additional geometry with partially embedded rotor similar to a channel wing is considered to increase the beneficial interaction. This paper shows the aerodynamic integration effects with a focus on climb performance and provides an assessment of the three aforementioned configurations for a simplified wing segment at takeoff conditions. Steady Reynolds-averaged Navier–Stokes simulations have been conducted using an actuator disk model and were evaluated based on the overall design. Interacting with the blown flap, the conventional tractor propeller induces large lift and drag increments due to the vectored sliptream. Although this effect is much smaller for an over-the-wing configuration, by halving the lift augmentation, the lift-to-drag ratio and the propulsive efficiency are considerably improved. Besides a moderate lift gain, the main advantage of a channel wing design is the location of the thrust vector close to the center of gravity resulting in a smaller nosedown pitching moment due to thrust. A disadvantage of over-the-wing propellers is the inhomogeneous inflow at higher velocity, which leads to oscillating blade loads and reduced efficiency.
Internet Linkhttp://arc.aiaa.org/doi/pdf/10.2514/1.C032307


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Autor(en) Müller, Lars | Kozulovic, Dragan | Radespiel, Rolf
TitelAerodynamic performance of an over-the-wing propeller configuration at increasing Mach number
HerausgeberCEAS Aeronautical Journal DOI 10.1007/s13272-014-0108-1 (online, to be printed soon) (Reviewed)
Erscheinungsjahr2014
Abstract
Over-the-wing propeller configurations and particularly channel wing concepts show increased climb performance, and through effective acoustic shielding, reduced noise emissions when compared to a conventional tractor configuration. The main aerodynamic mechanisms could be identified by steady flow simulations of a simplified wing geometry and actuator disk. At take-off, where the thrust coefficient is very high, the drag of the wing decreases much stronger than the thrust of the propeller. This paper investigates the cruise conditions where the thrust coefficient is by one order of magnitude lower. The numerical results give evidence that, even at a moderate flight Mach number of 0.6, the beneficial influence of the over-the-wing propeller on the drag coefficient of the wing is negligibly small. On the other hand, the amount of propeller efficiency that is lost through high inflow velocity above the wing increases with Ma due to compressibility effects. As a result, the propulsive efficiency of an over-the-wing configuration is 16 % smaller than the reference (tractor). Semi-empirical correlations show that even at very low Mach numbers a drawback of at least 5 % remains. Although repositioning the propeller at the wing trailing edge may recover 4 % of the propulsive efficiency at Ma = 0.6, it is not advisable to give up most of the noise-shielding effect at take-off which is an important advantage of the channel wing.
Internet Linkhttp://link.springer.com/article/10.1007%2Fs13272-014-0108-1


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Autor(en) Müller, Lars | Kozulovic, Dragan | Friedrichs, Jens
TitelUnsteady Flow Simulations of an Over-the-wing Propeller Configuration
HerausgeberProceedings of 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Cleveland
Erscheinungsjahr2014
Abstract
The aerodynamic integration effects of an embedded over-the-wing propeller at take-off conditions are discussed based on steady and unsteady Reynolds-averaged Navier-Stokes flow simulations. In contrast to the rotating blade and hub geometry, the steady computations utilized an actuator disk model with blade element theory enhancement to investigate the mutual influnce between installed propeller and wing with sufficient accuracy. A simplified high-lift geometry of this channel wing concept is compared to a conventional tractor configuration. While the general over-the-wing integration effects, such as lift-to-drag ratio improvement and deteriorated propeller efficiency, are already captured by inexpensive steady simulations, only unsteady computations with full propeller geometry reveal some important flow details. The most striking unsteady effect is the interaction of the blade tip vortex with the boundary layer of the wing which only occurs at the channel wing due to the close coupling. As a consequence the low momentum fluid detaches above the flap leading to a comparatively low lift coefficient.
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Autor(en) Krosche, Martin | Heinze, Wolfgang
TitelA Robustness Analysis of a Preliminary Design of a CESTOL Aircraft
HerausgeberInformatikbericht 2014-02, Institut für Wissenschaftliches Rechnen, Carl-Friedrich-Gauß-Fakultät, TU Braunschweig
Erscheinungsjahr2014
Abstract
As part of the Collaborative Research Center 880 preliminary aircraft design activities are carried out for a new class of low-noise cruise-efficient transport aircrafts with short take-off and landing capabilities (CESTOL). A corresponding aircraft is quite different from a state-of-the-art commercial aircraft because of the use of active high-lift devices. The fact that new technologies are not sufficiently understood yet in combination with the assumption of common design data and the use of classical calculation methods expresses itself in uncertainties which are of epistemic character. The robustness of a deterministic CESTOL aircraft design towards parameters such as the necessary engine thrust, direct operating costs, or the runway lengths is investigated here concerning the mentioned uncertainties. For this purpose a stochastic description of parameter variations of the design is formulated. Stochastic quantities are computed by Monte Carlo (MC) sampling to rate the robustness. A distributed component-based software implementation is used to perform the MC sampling. The software system is installed on a Linux cluster with several multi-CPU computers; a deterministic sample is simulated through the design program PrADO.
Internet Linkhttp://www.digibib.tu-bs.de/?docid=00055746


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Autor(en) Vechtel, Dennis | Meissner, Ute Marita | Hahn, Klaus-Uwe
TitelOn the use of a steerable main landing gear for crosswind landing assistance
HerausgeberCEAS Aeronautical Journal, ISSN 1869-5582 (Reviewed)
Erscheinungsjahr2014
Abstract
Several crosswind-related incidents show that landing under heavy crosswind conditions can be challenging for pilots and may pose a threat to aviation or at least lead to higher pilot workload and/or irregularities in operations. For transport aircraft the common approach technique for crosswind landings is the so-called crabbed approach with wings level and a windward heading correction. This technique requires alignment of the aircraft with the runway prior to touchdown in order to keep lateral loads of the landing gear and tyres as low as possible and to maintain the controllability on ground after touchdown. The German Aerospace Center Institute of Flight Systems has used the idea of steerable main gears and developed a crosswind landing assistance system. During approach all gear struts are automatically aligned with the runway so that no decrab manoeuvre is required. On ground the assistance system uses each steerable landing gear, differential braking, and the aerodynamic control surfaces to control and stabilise the aircraft. After touchdown the aircraft is automatically aligned with the runway centreline and the still existing crab angle is slowly reduced. A simulator study with pilots in the loop using a model of a typical medium range transport aircraft was conducted in order to evaluate the benefits of such a landing technique. The study revealed that not only the aircraft controllability could be improved by landing in crabbed motion under strong crosswind conditions, but that the side forces acting on the landing gear can be reduced significantly as well. It was also shown that the use of steerable main landing gears is able to enlarge the spectrum of autoland operations, which is relatively limited at present in terms of maximum allowable crosswinds. All together the system has shown to be able to improve flight safety, lower the risk of weather-related delays due to go-arounds or diversions, and it also reduces structural loads on the landing gear during touchdown and landing.
Internet Linkhttp://dx.doi.org/10.1007/s13272-014-0107-2


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Autor(en) Akkermans, Rinie | Pott-Pollenske, Michael | Buchholz, Heino | Delfs, Jan | Almoneit, Daniela
TitelInstallation Effects of a Propeller Mounted on a High-Lift Wing with a Coanda Flap. Part I: Aeroacoustic Experiments
Herausgeber20th AIAA/CEAS Aeroacoustics Conference, Atlanta, June 2014
Erscheinungsjahr2014
Abstract
In this contribution, we present aeroacoustic experiments concerning installation effects of propellers. Such installation effects are important as they can significantly alter the sound radiation as compared to an isolated propeller. For this purpose, detailed experiments have been conducted in the NWB aeroacoustic wind tunnel in Braunschweig, Germany. The considered geometry is a nine-bladed propeller installed in front of a high-lift wing (employing a Coanda flap). The results illustrate the influence of propeller rotational speed, blade pitch angle, wind tunnel velocity, and angle of attack variations on the sound radiation. Furthermore, with a source localisation technique insight is gained in the dominant sound sources, and reveals the importance of periodic as well as broadband noise for the considered geometry.


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Autor(en) Akkermans, Rinie | Ewert, Roland | Moghadam, Mohsen | Dierke, Juergen | Buchmann, Nadine
TitelTowards Overset LES Prediction of Sound Sources
Herausgeber5th Symposium on Hybrid RANS-LES Methods, Texas, March 2014
Erscheinungsjahr2014
Abstract
In this contribution, we present an application of a computational aeroacoustics code as a hybrid Zonal DNS tool. The extension of the Non-Linear Perturbation Equations (NLPE) with viscous terms is presented as well as information related to the numerical method. The applicability of the simulation tool is illustrated with two testcases, i.e., a circular cylinder in a uniform flow at moderate Reynolds numbers and a 3D decaying flow initialised with Taylor-Green vortices. Both testcases provide results which match well with data reported in literature. The cylinder testcase verifies that the viscous terms are indeed correctly implemented and the Taylor-Green vortex case illustrates that the numerical scheme introduced minimal numerical dissipation.


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Autor(en) Rosic, Bojana | Diekmann, Jobst Henning
TitelStochastic Description of Aircraft Simulation Models and Numerical Approaches
Herausgebersubmitted to AIAA
Erscheinungsjahr2014
Abstract
This paper is concerned with the uncertainty quantification of an aircraft simulation model. Mathematically speaking the aircraft model represents a system of second order differential equations dependent on a set of input parameters related to the mass, aerodynamics and the structure of the aircraft. The input aerodynamic parameters are modelled as random variables and processes whose probability distributions are chosen according to the maximum entropy principle and available experimental data. For a flight dynamics model the evolution of uncertainties in the aircraft state trajectory is estimated with the help of so-called non-intrusive numerical approaches, examples of which are the direct integration method, the stochastic collocation approach and the pseudo-Galerkin method. These numerical methods rely on a set of samples of aircraft state trajectories simply obtained by solving the corresponding systems of deterministic ordinary differential equations.
Internet Linkhttp://www.digibib.tu-bs.de/?docid=00055749


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Autor(en) Kucerova, Anna | Sykora, Jan | Rosic, Bojana | Matthies, Hermann
TitelAcceleration of uncertainty updating in the description of transport processes in heterogeneous materials
HerausgeberJournal of Computational and Applied Mathematics 236 (2012) 4862–4872
Erscheinungsjahr2014
Abstract
The prediction of thermo-mechanical behaviour of heterogeneous materials such as heat and moisture transport is strongly influenced by the uncertainty in parameters. Such materials occur e.g., in historic buildings, and the durability assessment of these therefore needs a reliable and probabilistic simulation of transport processes, which is related to the suitable identification of material parameters. In order to include expert knowledge as well as experimental results, one can employ an updating procedure such as Bayesian inference. The classical probabilistic setting of the identification process in Bayes’ form requires the solution of a stochastic forward problem via computationally expensive sampling techniques, which makes the method almost impractical. In this paper novel stochastic computational techniques such as the stochastic Galerkin method are applied in order to accelerate the updating procedure. The idea is to replace the computationally expensive forward simulation via the conventional finite element (FE) method by the evaluation of a polynomial chaos expansion (PCE). Such an approximation of the FE model for the forward simulation perfectly suits the Bayesian updating. The presented uncertainty updating techniques are applied to the numerical model of coupled heat and moisture transport in heterogeneous materials with spatially varying coefficients defined by random fields.
Internet Linkhttp://www.sciencedirect.com/science/article/pii/S037704271200060X


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Autor(en) Rosic, Bojana | Litvinenko, Alexander | Pajonk, Oliver | Matthies, Hermann
TitelSampling-free linear Bayesian update of polynomial chaos representations
HerausgeberJournal of Computational Physics 231 (2012) 5761–5787
Erscheinungsjahr2014
Abstract
We present a fully deterministic approach to a probabilistic interpretation of inverse prob- lems in which unknown quantities are represented by random fields or processes, described by possibly non-Gaussian distributions. The description of the introduced ran- dom fields is given in a ‘‘white noise’’ framework, which enables us to solve the stochastic forward problem through Galerkin projection onto polynomial chaos. With the help of such a representation the probabilistic identification problem is cast in a polynomial chaos expansion setting and the Baye’s linear form of updating. By introducing the Hermite alge- bra this becomes a direct, purely algebraic way of computing the posterior, which is com- paratively inexpensive to evaluate. In addition, we show that the well-known Kalman filter is the low order part of this update. The proposed method is here tested on a stationary diffusion equation with prescribed source terms, characterised by an uncertain conductiv- ity parameter which is then identified from limited and noisy data obtained by a measure- ment of the diffusing quantity. Ó 2012 Elsevier Inc. All rights reserved.
Internet Linkhttp://www.sciencedirect.com/science/article/pii/S0021999112002483


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Autor(en) Pajonk, Oliver | Rosic, Bojana | Litvinenko, Alexander | Matthies, Hermann
TitelA deterministic filter for non-Gaussian Bayesian estimation— Applications to dynamical system estimation with noisy measurements
HerausgeberPhysica D 241 (2012) 775–788
Erscheinungsjahr2014
Abstract
We present a fully deterministic method to compute sequential updates for stochastic state estimates of dynamic models from noisy measurements. It does not need any assumptions about the type of distribution for either data or measurement—in particular it does not have to assume any of them as Gaussian. Here the implementation is based on a polynomial chaos expansion (PCE) of the stochastic variables of the model—however, any other orthogonal basis would do. We use a minimum variance estimator that combines an a priori state estimate and noisy measurements in a Bayesian way. For computational purposes, the update equation is projected onto a finite-dimensional PCE-subspace. The resulting Kalman-type update formula for the PCE coefficients can be efficiently computed solely within the PCE. As it does not rely on sampling, the method is deterministic, robust, and fast. In this paper we discuss the theory and practical implementation of the method. The original Kalman filter is shown to be a low-order special case. In a first experiment, we perform a bi-modal identification using noisy measurements. Additionally, we provide numerical experiments by applying it to the well known Lorenz-84 model and compare it to a related method, the ensemble Kalman filter. © 2012 Elsevier B.V. All rights reserved.
Internet Linkhttp://www.sciencedirect.com/science/article/pii/S0167278912000036


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Autor(en) Rosic, Bojana | Kucerova, Anna | Sykora, Jan | Pajonk, Oliver | Litvinenko, Alexander | Matthies, Hermann G.
TitelParameter identification in a probabilistic setting
HerausgeberEngineering Structures, Volume 50, May 2013, Pages 179-196 (Reviewed)
Erscheinungsjahr2014
Abstract
The parameters to be identified are described as random variables, the randomness reflecting the uncer- tainty about the true values, allowing the incorporation of new information through Bayes’s theorem. Such a description has two constituents, the measurable function or random variable, and the probability measure. One group of methods updates the measure, the other group changes the function. We connect both with methods of spectral representation of stochastic problems, and introduce a computational pro- cedure without any sampling which works completely deterministically, and is fast and reliable. Some examples we show have highly nonlinear and non-smooth behaviour and use non-Gaussian measures.
Internet Linkhttp://www.sciencedirect.com/science/article/pii/S0141029612006426


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Autor(en) Pajonk, Oliver | Rosic, Bojana | Matthies, Hermann G.
TitelSampling-free linear Bayesian updating of model state and parameters using a square root approach
HerausgeberComputers & Geosciences, Volume 55, June 2013, Pages 70-83
Erscheinungsjahr2014
Abstract
We present a sampling-free implementation of a linear Bayesian filter based on a square root formulation. It employs spectral series expansions of the involved random variables, one such example being Wiener's polynomial chaos. The method is compared to several related methods, as well as a full Bayesian update, on a simple scalar example. Additionally it is applied to a combined state and parameter estimation problem for a chaotic system, the well-known Lorenz-63 model. There, we compare it to the ensemble square root filter (EnSRF), which is essentially a probabilistic implementation of the same underlying estimator. The spectral method is found to be more robust than the probabilistic one, especially for variance estimation. This is to be expected due to the sampling-free implementation.
Internet Linkhttp://www.sciencedirect.com/science/article/pii/S0098300412001732


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Autor(en) Ewert, Roland | Dierke, Jürgen | Neifeld, Andrej | Alavi Moghadam, Seyed Mohsen
TitelLinear and Non-Linear Perturbation Equations with Relaxation Source Terms for Forced Eddy Simulation of Aeroacoustic Sound Generation
Herausgeber20th AIAA/CEAS Aeroacoustics Conference Atlanta, Georgia, 2014 (Reviewed)
Erscheinungsjahr2014
Abstract
Turbulence related sound is generated by the dynamics of fluctuating vorticity. For example, trailing edge noise is caused by vorticity traveling past the trailing edge. To excite fluctuating vorticity by forcing the linearized Euler equations (LEE) with right-hand side source terms, one peculiar problem is observable: while the rise of vorticity levels by external sources poses no problem, to properly lower them, the right-hand side terms must act as a sink, being exactly in anti-phase to the vorticity levels as present in the LEE solution. However, the accurate prediction of vorticity in terms of phase cannot be guaranteed, especially for approximately modeled sources e.g. using stochastic methods. Thus in general there will be a mismatch between actual induced and intended levels of vorticity. In this paper a new class of relaxation source terms is introduced that enables the proper excitation of vorticity levels in linear and non-linear perturbation equations and as such enables an accurate control over the vorticity magnitudes. The source can be formulated to act selectively in wave-number space, i.e. without directly affecting the dynamics of resolved low wave-number vorticity components whereas the resolved high wave number part is piloted by the uctuating vorticity imposed as a reference solution. The reformulation of the Navier-Stokes equations in primitive variables and non-linear perturbation form is presented. Direct noise computation of sound radiated from a vortex shedding cylinder in laminar cross flow verify their implementation. The relaxation source term without forcing is applied to the unstable jet problem of the 4th CAA Workshop on Benchmark Problems. The forcing of frozen and decaying stochastic turbulence in conjunction with the relaxation source term is studied. First results for high-lift noise prediction with forced eddy simulation are presented.


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Autor(en) Herr, Michaela | Rossignol, Karl-Stephane | Delfs, Jan | Lippitz, Nicolas | Mößner, Michael
TitelSpecification of Porous Materials for Low-Noise Trailing-Edge Applications
Herausgeber20th AIAA/CEAS Aeroacoustics Conference Atlanta, Georgia, 2014 (Reviewed)
Erscheinungsjahr2014
Abstract
Systematic testing of the microstructural and aeroacoustic properties of porous metals applicable as low-noise trailing-edge (TE) treatments has been initiated within the Collaborative Research Center SFB 880 Fundamentals of High-Lift for Future Civil Aircraft. Generic TE noise experiments were performed at Re = 800,000 to 1,200,000 in DLR's open-jet AWB facility. Complementary flow measurements in the closed test section MUB wind-tunnel of the TU Braunschweig served to quantify the induced aerodynamic effects. The presented database forms part of an ongoing cumulative effort, combining experimental and numerical methods, to gain a deeper understanding of the prevalent TE noise reduction mechanisms. For the large variety of porous materials tested herein a clear dependence of the achieved broadband noise reduction (reaching 2{6 dB at maximum) on the flow resistivity was identified. Basic design recommendations for material resistivity and pore sizes, the latter to minimize high-frequency self-noise contributions, were deduced for low-noise TE applications. An acoustic nearfield pressure release across the porous region, adversely coupled with a loss in lift performance for porous TE replacements, appears as the major noise-reduction requirement.


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Autor(en) Faßmann, Benjamin | Rautmann, Christof | Ewert, Roland | Delfs, Jan
TitelEfficient prediction of broadband trailing edge noise and application to porous edge treatment
HerausgeberInternational Journal of Aeroacoustic ISSN 1475-472X -- Special Issue on Windturbine Noise
Erscheinungsjahr2014
Abstract
Trailing edge noise generated by turbulent flow traveling past an edge of an airfoil (TBL-TEN) represents one of the most essential paradigms of aeroacoustic sound generation at solid surfaces. It is of great interest for noise problems in various areas of technical application. First principle based Computational Aeroacoustics (CAA) methods with short response time are needed in the industrial design process for reliable prediction of spectral differences in TBL-TEN due to design modifications. In this work an aeroacoustic method is studied that rests on a hybrid two-step CFD/CAA procedure. In a first step Reynolds Averaged Navier-Stokes simulation provides the time-averaged solution to the turbulent flow, including the mean-flow and turbulence statistics such as length- and time-scales and turbulence kinetic energy. Fluctuating sound sources are stochastically generated from RANS statistics with the Fast Random Particle-Mesh Method (FRPM) to simulate in a second CAA step broadband aeroacoustic sound. From experimental findings it is well known that porous trailing edges significantly lower trailing edge noise level over a large bandwidth of frequencies reaching 6 to 8dB reduction. Furthermore, sound reduction depends on the porous material parameters, e.g. geometry, porosity, permeability and pore size. This paper presents first results for the extended hybrid CFD/CAA method to include the effect on noise of porous materials with specifically prescribed parameters. To incorporate the effect of porosity, an extended formulation of the Acoustic Perturbation Equations (APE) with source terms is derived based on a reformulation of the volume averaged Navier-Stokes equations into perturbation form. Proper implementation of the Darcy and Forchheimer terms is verified for sound propagation in homogeneous and anisotropic porous medium. Sound generation is studied for a generic symmetric NACA0012 airfoil without lift to separate secondary effects of lift and camber on sound from those of the basic edge noise treatments. The reference solid airfoil configurations are compared with published experimental data. Convincing agreement in the prediction of one-third-octave band spectra is found. Simulation with porous edge treatment reveals a broadband noise reduction capability of approximately 6dB with similar trends as seen in experiment.


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Autor(en) Keller, Dennis | Rudnik , Ralf
TitelNumerical Investigation of Engine Effects on a Transport Aircraft with Circulation Control
HerausgeberJournal of Aircraft, tbd (Reviewed)
Erscheinungsjahr2014
Abstract
The scope of this paper is to illustrate the installation effects of a turboprop engine on a high-lift configuration of a short take off and landing (STOL) aircraft with circulation control. In addition to the influence on the wing performance, the impact on the longitudinal static stability of the aircraft is also investigated. Furthermore, critical failure cases, namely extit{one engine inoperative} (OEI), as well as an asymmetric circulation control failure, are assessed. Therefore, steady CFD calculations based on the Reynolds-averaged Navier-Stokes (RANS) equations were performed. The propeller is modeled with an actuator disk approach. The results show strong potential of increasing lift by synergy effects between circulation control and propeller slipstream. However, the longitudinal stability and controllability are adversely affected. Regarding the case of OEI, the resulting yawing moments are twice as high as the actual yawing moments from the asymmetric thrust and therefore higher than expected.


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Autor(en) Sinapius, Michael | Monner, Hans Peter | Riemenschneider, Johannes | Kintscher, Markus
TitelDLRs morphing wing activities within the European network
HerausgeberProcedia IUTAM 10, pp. 416 – 426
Erscheinungsjahr2014
Abstract
Smart Structures technology called Adaptronics in Germany covers the entire field of making the elastomechanicalbehaviour of structures adaptable. The main objectives are vibration control, noise reduction and shape control. The latter is directly related to morphing of airframes, thus being a focus of DLR’s aeronautical research program. DLR initiated the national morphing wing activities in the mid-nineties with research projects on morphing wing trailing egdes. The lessons learned where exploited continuously in different national and international projects up today. The research covers the most relevant application scenarios of morphing like smart trailing egde, smart winglet, or smart leading egde including the smart slat. Presently the gapless droop nose for laminar wings of future civil transport aircrafts is in the focus of the investigations at DLR in collaboration with European partners. This paper gives a survey of the related national and international activities where DLR has been involved in since the mid-nineties and elaborates the challenge of designing morphing wing structures, i.e. to provide flexibility for the deformation andstiffness for carrying high loads at the same time.
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Autor(en) Beutel, Tobias | Sattler, Stefan | El Sayed, Yosef | Schwerter, Martin | Zander, Martin | Büttgenbach, Stephanus | Leester-Schädel, Monika | Radespiel, Rolf | Sinapius, Michael | Radespiel, Rolf
TitelDesign of a high-lift experiment in water including active flow control
HerausgeberSmart Materials and Structures, Vol. 23 , 077004 (10pp) (Reviewed)
Erscheinungsjahr2014
Abstract
This paper describes the structural design of an active flow-control experiment. The aim of the experiment is to investigate the increase in efficiency of an internally blown Coanda flap using unsteady blowing. The system uses tailor-made microelectromechanical (MEMS) pressure sensors to determine the state of the oncoming flow and an actuated lip to regulate the mass flow and velocity of a stream near a wall over the internally blown flap. Sensors and actuators are integrated into a highly loaded system that is extremely compact. The sensors are connected to a bus system that feeds the data into a real-time control system. The piezoelectric actuators using the d33 effect at a comparable low voltage of 120 V are integrated into a lip that controls the blowout slot height. The system is designed for closed-loop control that efficiently avoids flow separation on the Coanda flap. The setup is designed for water-tunnel experiments in order to reduce the free-stream velocity and the system’s control frequency by a factor of 10 compared with that in air. This paper outlines the function and verification of the system’s main components and their development.
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Autor(en) Delfs, Jan | Faßmann, Benjamin | Lippitz, Nicolas | Mößner, Michael | Müller, Lars | Rurkowska, Katherina
TitelSFB 880 – AEROACOUSTIC RESEARCH FOR LOW NOISE TAKE-OFF AND LANDING
HerausgeberCEAS Aeronautical Journal (Reviewed)
Erscheinungsjahr2014
Abstract
This paper gives an overview about prediction capabilities and the development of noise reduction technologies appropriate to reduce high lift noise and propeller noise radiation for future low noise transport aircraft with short take-off and landing capabilities. The work is embedded in the collaborative research centre SFB880 in Braunschweig, Germany. Results are presented from all the acoustics related projects of SFB880 which cover the aeroacoustic simulation of the effect of flow permeable materials, the characterization, development, manufacturing and operation of (porous) materials especially tailored to aeroacoustics, new propeller arrangements for minimum exterior noise due to acoustic shielding as well as the prediction of vibration excitation of aircraft structures, reduced by porous materials.
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Internet Linkhttp://dx.doi.org/10.1007/s13272-014-0115-2


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Autor(en) Schwerter, Martin | Behr, Christian | Leester-Schädel, Monika | Wierach, Peter | Sinapius, Michael | Büttgenbach, Stephanus | Dietzel, Andreas
TitelStress-unsusceptible pressure sensors embedded in fiber composite
HerausgeberProceedings of Eurosensors 2014, Brescia, 2014
Erscheinungsjahr2014
Abstract
This paper discusses the integration of pressure sensors into flow sensing airfoils made of fiber composite material to be used in future aircraft. An embedding procedure for damage-free integration is described, in which the sensors experience stresses by vacuum and curing during the integration at composite lamination. The mechanical characteristics and the influences of external mechanical stresses on the integrated sensor are further investigated. A sensor design unsusceptible to external mechanical stresses parallel to the air wing surface is proposed and verified by tensile stress tests.
Internet Linkhttp://www.sciencedirect.com/science/article/pii/S1877705814027131


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Autor(en) Mößner, Michael | Radespiel, Rolf
TitelFlow Simulations over Porous Media - Comparisons with Experiments
HerausgeberICCFD8, Chengdu, China, 2014
Erscheinungsjahr2014
Abstract
A closure model is presented to compute turbulent flow over and through porous media. The model is based on the Darcy and Forchheimer term which are also applied to a Reynolds-stress turbulence model. The implementation of the model into a flow solver is validated with wind-tunnel experiments of a 2D-wing with a porous trailing edge. Pressure and PIV measurements are performed for the determination of integral force coefficients and the understanding of the detailed flow field. The measurement data are discussed and compared with the results of the numerical computations. The simulations match the experiments very well and reproduce the flow phenomena correctly. This yields confidence for using the closure model for more general applications.
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Internet Linkhttp://myocean060920001.my08.w001.vhost012.cn/images/file/20140813163543024302.zip


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Autor(en) Schwerter, Martin | Behr, Christian | Leester-Schädel, Monika | Wierach, Peter | Sinapius, Michael | Büttgenbach, Stephanus | Dietzel, Andreas
TitelMEMS Pressure Sensors Embedded into Fiber Composite Airfoils
HerausgeberProceedings of IEEE Sensors, Valencia, 2014
Erscheinungsjahr2014
Abstract
The paper describes the integration of pressure sensors into fiber composite in order to obtain flow sensing airfoils to be used in future aircrafts. First, the sensor design and working principle is described, followed by an embedding procedure for damage-free integration. Here the sensors are faced to stresses by vacuum and curing during the embedding process into fiber-reinforced plastic. The mechanical characteristics and the influence of external mechanical stresses on the integrated sensor are further investigated. Finally, a sensor design unsusceptible to external mechanical stresses parallel to the surface of the airfoil is proposed and verified by tensile stress tests.
Internet Linkhttp://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6985052&tag=1


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Autor(en)Diekmann, Jobst Henning
TitelAnalysis of trimmable conditions for a civil aircraft with active high-lift system
HerausgeberCEAS Aeronautical Journal, Springer Verlag, Wien, 2014 (Reviewed)
Erscheinungsjahr2014
Abstract
This paper outlines recent flight dynamic analysis results of a civil aircraft with active high-lift system using blown Coanda flaps. The main focus lies in the trim analysis of the aircraft. Therefore, the basic structure and core elements of the nonlinear model, describing the dynamic behavior of an aircraft with this specific type of active high-lift system are presented. The center of gravity range allowing controllability and static stability of the aircraft is determined, and the resulting characteristics of the aerodynamic model and their impact on the trim results of the aircraft are analyzed. The results show specific flight dynamic difficulties related to the active high-lift system, namely in the flying characteristics necessary for safe take-off and approach procedures. The flight physics are explained and discussed. The necessity of the application of a wing leading edge device is outlined by preliminary studies and further remedial means are proposed.
Internet Linkhttp://link.springer.com/article/10.1007/s13272-014-0132-1


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Autor(en) Teichel, Sönke | Dörbaum, Michael | Misir, Onur | Merkert, Arvid | Mertens, Alex | Seume, Jörg | Ponick, Bernd
TitelDesign Considerations for the Components of Electrically Powered Active High-Lift-Systems in Civil Aircraft
HerausgeberCEAS Aeronautical Journal, ISSN: 1869-5582, CEAS Aeronaut J, DOI: 10.1007/s13272-014-0124-1 (Reviewed)
Erscheinungsjahr2014
Abstract
To address the challenges of future air traffic, such as more accessible air travel with better public cceptance, this research work focuses on efficient active high-lift systems (AHLS). This system applies boundary layer suction combined with a controlled Coanda jet. Electrically powered compressors are located in the wings at each flap to supply the suction and blowing air mass flow rate to the AHLS, thus coupling the two in a useful way. This concept provides flexibility and controllability of lift generation and is consistent with the trend towards an "all-electric aircraft". General models for assessment of such systems in preliminary aircraft design are not available yet as they require interdisciplinary expertise. This paper provides general design considerations for the components of this type of electrically powered AHLS, comprising compressors, motors, power electronics, system peripherals, and generators. The conceptual design for those components results in models for preliminary aircraft design which allow estimating power consumption, size and mass.


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Autor(en)Wiegel, Julian
TitelStudent Assistant - Simulation of Aircraft Noise
HerausgeberThird Symposium on "Simulation of Wing and Nacelle Stall", Braunschweig, Germany, June 2012
Erscheinungsjahr2014
Abstract
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Autor(en)Wiegel, Julian
TitelModification of a compressor test rig for measuring the influence of inlet distortions on the compressor flow
HerausgeberThird Symposium on "Simulation of Wing and Nacelle Stall", Braunschweig, Germany, June 2012
Erscheinungsjahr2014
Abstract
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Autor(en)Wiegel, Julian
TitelStudent Assistant - Simulation of Aircraft Noise
HerausgeberThird Symposium on "Simulation of Wing and Nacelle Stall", Braunschweig, Germany, June 2012
Erscheinungsjahr2014
Abstract
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Autor(en)Wiegel, Julian
TitelStudent Assistant - Simulation of Aircraft Noise
HerausgeberThird Symposium on "Simulation of Wing and Nacelle Stall", Braunschweig, Germany, June 2012
Erscheinungsjahr2014
Abstract
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Autor(en)Wiegel, Julian
TitelStudent Assistant - Simulation of Aircraft Noise
HerausgeberThird Symposium on "Simulation of Wing and Nacelle Stall", Braunschweig, Germany, June 2012
Erscheinungsjahr2014
Abstract
dfsg sdf g df g sdf dfgggggggggggggggggggggggggggggggggggg
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Autor(en) Teichel, Sönke | Radespiel, Rolf | Burnazzi, Marco | Dietzel, Andreas | Leester-Schädel, Monika | Schwerter, Martin | Sinapius, Michael | Behr, Christian | Monner, Hans Peter | Rudenko, Anton | Horst, Peter | Schmitz, Andre | Ponick, Bernd | Dörbaum, Michael | Mertens, Axel | Merkert, Arvid | Friedrichs, Jens | Atalayer, Caglar | Seume, Jörg
TitelSFB 880 - Efficient High Lift
Herausgeber978-3-8440-3319-9, Proceedings of the 5th International Workshop on Aircraft System Technologies, Hamburg, February 24-25, 2015
Erscheinungsjahr2014
Abstract
The collaborative research centre (SFB) 880 investigates the fundamentals of high-lift generation for future civil aircraft, focusing on the fields of aero acoustics, lift generation and flight dynamics. This paper presents the research on lift generation in the years 2011 through 2014. The underlying research hypothesis of this work is that a further significant increase in lift generation of civil aircraft compared to the current state technology is possible using active lift systems. The investigated high-lift concept utilizes a combination of internally blown flaps and circulation control to achieve high flow turning at the wing. A flexible leading edge device for the wing without gap or step is designed to reduce noise generation and to increase the efficiency of the active blowing system. The overall objective of the project is to design an active lift system which requires a minimum of additional engine power to generate the required lift. A multidisciplinary collaborative approach was taken, combining the fields of aerodynamics, material science, microtechnology, turbomachinery and electrical engineering, increasing the efficiency of the active high-lift system by 75% compared to the baseline systems.


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Autor(en) Burnazzi, Marco | Radespiel, Rolf
TitelDesign and Analysis of a Droop Nose for Coanda Flap Applications
HerausgeberAIAA JOURNAL OF AIRCRAFT Vol. 51, No. 5, DOI: 10.2514/1.C032434 (Reviewed)
Erscheinungsjahr2014
Abstract
The present study describes the fundamentals of droop nose design for improving the aerodynamics of airfoils with active high-lift using an internally blown Coanda-type flap. The main objectives are to increase the stall angle of attack and reduce the power required by the high-lift system. A two-dimensional sensitivity analysis explores the effects of varying airfoil camber and thickness in the first 20% of the chord. The resulting droop nose configuration improves the maximum lift coefficient by about 20% and increases the stall angle of attack by around 10–15 deg. A target lift coefficient of about 4.7 is reached with 28% less jet momentum coefficient, compared to the clean nose. As the modified leading-edge geometry presents different stall mechanisms, the aerodynamic response to variations of jet momentum is also different. In particular, for a jet momentum coefficient above 0.035, the stall angle of attack increases with jet momentum, in contrast with the behavior observed with the clean nose.
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Internet Linkhttp://arc.aiaa.org/doi/abs/10.2514/1.C032434


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Autor(en) Burnazzi, Marco | Radespiel, Rolf
TitelAssessment of leading-edge devices for stall delay on an airfoil with active circulation control
HerausgeberCEAS Aeronaut J (2014) 5:359–385 DOI 10.1007/s13272-014-0112-5 (Reviewed)
Erscheinungsjahr2014
Abstract
The use of active, internally blown high-lift flaps causes the reduction of the stall angle of attack, because of the strong suction peak generated at the leading-edge. This problem is usually addressed by employing movable leading-edge devices, which improve the pressure distribution, increase the stall angle of attack, and also enhance the maximum lift coefficient. Classical leading-edge devices are the hinged droop nose or the more effective slat with a gap. The flow distortions generated by the gap become an important source of noise during approach and landing phases. Based on these considerations, the present work aims at evaluating the potentials of gap-less droop nose devices designed for improving the aerodynamics of airfoils with active high lift. Both conventional leading-edge flaps and flexible droop noses are investigated. Flexible droop nose configurations are obtained by smoothly morphing the baseline leading-edge shape. Increasing the stall angle of attack and reducing the power required by the active high-lift system are the main objectives. The sensitivities of the investigated geometries are described, as well as the physical phenomena that rule the aerodynamic performance. The most promising droop-nose configurations are compared with a conventional slat device as well as with the clean leading-edge. The response of the different configurations to different blowing rates and angles of attack are compared and the stalling mechanisms are analyzed.
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Internet Linkhttp://link.springer.com/article/10.1007%2Fs13272-014-0112-5


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Autor(en) Burnazzi, Marco | Radespiel, Rolf
TitelSynergies between suction and blowing for active high-lift flaps
HerausgeberCEAS Aeronaut Journal, DOI 10.1007/s13272-014-0146-8 (Reviewed)
Erscheinungsjahr2014
Abstract
The present 2-D CFD study investigates aero- dynamic means for improving the power efficiency of an active high-lift system for commercial aircraft. The high- lift configuration consists of a simple-hinged active Coanda flap, a suction slot, and a flexible droop nose device. The power required to implement circulation control is pro- vided by electrically driven compact compressors posi- tioned along the wing behind the wingbox. The compact compressors receive air from the suction slot, which also represents an opportunity to increase the aerodynamic performance of the airfoil. The present work investigates the aerodynamic sensitivities of shape and location of the suction slot in relation to the maximum lift performance of the airfoil. The main purpose of the study is the reduction of the compressor power required to achieve a target lift coefficient. The compressor power requirements can be reduced in two ways: obtaining a high total pressure at the end of the suction duct (compressor inlet) and reducing the momentum needed by the Coanda jet to avoid flow sepa- ration from the flap. These two objectives define the guideline of the suction slot design. As a result, a jet momentum reduction of 16 % was achieved for a target lift coefficient of 5 with respect to the same configuration without suction. Furthermore, the study yielded physical insight into the aerodynamic interaction between the two active flow control devices.
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Internet Linkhttp://link.springer.com/article/10.1007%2Fs13272-014-0146-8


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Autor(en) Burnazzi, Marco | Kumar, Pradeep | Semaan, Richard | Radespiel, Rolf
TitelNUMERICAL ASSESSMENT OF TWO PERIODIC ACTUATION APPROACHES FOR FLOW SEPARATION CONTROL
HerausgeberDLRK Kongress, 2014, Augsburg
Erscheinungsjahr2014
Abstract
This study investigates two actuation approaches to implement periodic tangential blowing over a gap-less high-lift flap. The high-lift configuration is composed of an active simple-hinged Coanda flap and a leading-edge droop nose device. The two approaches compared in the present work are based on different methods for obtaining a periodic oscillation of the Coanda jet. The first approach varies the jet momentum by periodically changing the slot exit section. As a result the jet velocity remains approximately constant and the mass flow drives the momentum oscillations. In the second approach, the total pressure inside the jet plenum is varied, leading to different jet velocities and mass flows. These two approaches create jets with different characteristics, which interact differently with the flow over the flap. The analysis is based on flow-field data obtained from 2D unsteady Reynolds averaged Navier-Stokes (uRANS) simulations. The two actuation approaches are compared for two different frequencies and two different amplitudes. The results show that similar flow mechanisms are obtained by the two approaches, and the resulting lift performances are comparable. However, in the case of large amplitude signals the lip-motion approach lead to smaller fluctuations of lift coefficient and to a slightly higher average lift.
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Autor(en)Müller, Lars
TitelAerodynamic Performance of an Over-the-wing Propeller Configuration at Increasing Mach Number
HerausgeberCEAS Aeronautical Journal, Vol. 5, No. 3, pp. 305-317 (Reviewed)
Erscheinungsjahr2014
Abstract
Over-the-wing propeller configurations and particularly channel wing concepts show increased climb performance, and through effective acoustic shielding, reduced noise emissions when compared to a conventional tractor configuration. The main aerodynamic mechanisms could be identified by steady flow simulations of a simplified wing geometry and actuator disk. At take-off, where the thrust coefficient is very high, the drag of the wing decreases much stronger than the thrust of the propeller.This paper investigates the cruise conditions where the thrust coefficient is by one order ofmagnitude lower. The numerical results give evidence that, even at a moderate flight Mach number of 0.6, the beneficial influence of the over-the-wing propeller on the drag coefficient of the wing is negligibly small. On the other hand, the amount of propeller efficiency that is lost through high inflow velocity above the wing increases with Ma due to compressibility effects. As a result, the propulsive efficiency of an over-the-wing configuration is 16 % smaller than the reference (tractor). Semi-empirical correlations showthat even at very lowMach numbers a drawback of at least 5 %remains. Although repositioning the propeller at the wing trailing edge may recover 4 % of the propulsive efficiency atMa = 0.6, it is not advisable to give up most of the noise-shielding effect at take-off which is an important advantage of the channel wing.
Internet Linksftp://apollo.pfi.ing.tu-bs.de//home/fex/auswaertig/lmuellersfb/publications/2013/CEAS-AJ_2014_Mueller_full


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Autor(en)Müller, Lars
TitelUnsteady Flow Simulations of an Over-the-Wing Propeller Configuration
Herausgeber50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, No. AIAA 2014-3886, Cleveland, Ohio
Erscheinungsjahr2014
Abstract
The aerodynamic integration effects of an embedded over-the-wing propeller at take-off conditions are discussed based on steady and unsteady Reynolds-averaged Navier-Stokes flow simulations. In contrast to the rotating blade and hub geometry, the steady computations utilized an actuator disk model with blade element theory enhancement to investigate the mutual influnce between installed propeller and wing with sufficient accuracy. A simplified high-lift geometry of this channel wing concept is compared to a conventional tractor configuration. While the general overthe- wing integration effects, such as lift-to-drag ratio improvement and deteriorated propeller efficiency, are already captured by inexpensive steady simulations, only unsteady computations with full propeller geometry reveal some important flow details. The most striking unsteady effect is the interaction of the blade tip vortex with the boundary layer of the wing which only occurs at the channel wing due to the close coupling. As a consequence the low momentum fluid detaches above the flap leading to a comparatively low lift coefficient.
Internet Linksftp://apollo.pfi.ing.tu-bs.de//home/fex/auswaertig/lmuellersfb/publications/2014/AIAA-JPC_2014_Mueller_full


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Autor(en) Burnazzi, Marco | Radespiel, Rolf
TitelDesign of a Droopnose Configuration for a Coanda Active Flap Application
Herausgeber51th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, Dallas (TX), AIAA 2013-0487
Erscheinungsjahr2013
Abstract
The present study describes the fundamentals of droopnose design for improving the aerodynamics of airfoils with active high-lift using a Coanda flap. Increasing the stall angle of attack and reducing the power required by the high-lift system, are the main objectives. The sensitivities of the investigated geometries are described, as well as the physical phenomena that rule the aerodynamic performance.
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Autor(en) Mößner, Michael | Radespiel, Rolf
TitelNumerical Simulations of Turbulent Flow over Porous Media
Herausgeber43rd AIAA Fluid Dynamics Conference and Exhibit, San Diego, California, 2013
Erscheinungsjahr2013
Abstract
A strategy to extending RANS solvers for simulating compressible and turbulent flow into and through porous media is presented. Therefor Darcy and Forchheimer term are appended to the Navier-Stokes equations. Beside of that the effect of porous terms onto the turbulence equations are considered. The interface region between porous and nonporous flow is modelled by an isentropic flow change and corrected by a stress jump condition. The implementation into the flow solver is demonstrated and verified with reference cases. Finally, solutions for a turbulent channel partially filled with cubes are compared with DNS computations.
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Autor(en) Krukow, Ian | Dinkler, Dieter
TitelA reduced-order model for aeroelastic studies on airfoils with active high-lift devices
HerausgeberInternational Forum on Aeroelasticity and Structural Dynamics, Bristol, UK
Erscheinungsjahr2013
Abstract
The application of circulation control allows shortening of runways which can be significant in particular cases. To study its influence on the aeroelastic behaviour of the airfoil, a simplified computational model is developed, which allows for systematic parameter variations. The model is based on modal reduction of the airfoil structure. An unsteady aerodynamic model is applied based on the results of numerical flow simulations. Investigation of aeroelastic stability leads to the usual phenomena of a conventional airfoil. Additionally, bending flutter occurs at high blowing rates of the Coanda stream and low velocities.


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Autor(en) Müller, Lars | Kozulovic, Dragan | Radespiel, Rolf
TitelAerodynamic Performance of an Over-thewing Propeller Configuration at Increasing Mach Number
HerausgeberProc. Deutscher Luft- und Raumfahrtkongress, Stuttgart, Germany
Erscheinungsjahr2013
Abstract
Over-the-wing propeller configurations show increased climb performance and, through effective acoustic shielding, reduced noise emissions when compared to a conventional tractor configuration. The main aero-dynamic mechanisms could be identified by steady flow simulations of a simplified geometry and actuator disk. At takeoff, where the thrust coefficient is very high, the drag of the wing decreases much stronger than the thrust of the propeller. This paper investigates the cruise conditions where the thrust coefficient is by one order of magnitude lower. The numerical results give evidence that, at a moderate flight Mach number of 0.6, the beneficial influence of the over-the-wing propeller on the drag coefficient of the wing is negligibly small. On the other hand, the propeller loses an even larger relative amount of efficiency due to compressibility effects on the inflow velocity above the wing. As a result, the propulsive efficiency of a channel wing configu-ration is 16% smaller than the tractor value, increasing the fuel consumption by a similar percentage. Semi-empirical correlations show that, even at very low Mach numbers, a drawback of at least 5% remains. How-ever, improvements concerning the propeller position and wing shape indicate a potential to restore two thirds of the performance loss.
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Autor(en) Lippitz, Nicolas | Rurkowska, Katherina | Rösler, Joachim | Langer, Sabine
TitelFouling Behaviour of Porous Metals
HerausgeberMetFoam, Raleigh, NC, 2013
Erscheinungsjahr2013
Abstract
Applications for porous materials range from structural materials to filters and acoustic absorbers. In many of these applications, e.g. silencers or air filters, the porous material is exposed to dirt. Fouling of filter materials and acoustic absorbers can change their characteristics by blocking pores, changing the pore morphology and decreasing the porosity. As parameters like trade efficiency and flow resistivity, that are important for the functionality of filters and acoustic absorbers, depend on the porosity and pore morphology, the fouling behaviour of porous materials is of major interest. In this study porous metals with different pore morphologies and porosities are investigated, such as microperforated panels, sintered fibre felts, metal foams and nanoporous superalloy membranes. The materials are mounted on a roof rack and polluted for a period of one year. The samples are periodically examined for changes in geometrical characteristics and flow resistivity. Additionally one half of the samples is washed to investigate the possibility of restoring the original characteristics. The materials are characterized using three dimensional CT-images as well as two dimensional microscopy images. Finally the correlation of geometrical characteristics, fouling behaviour and flow resistivity is outlined.


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Autor(en) Rurkowska, Katherina | Langer, Sabine
TitelCoupling elastic-poroelastic material in structure-borne sound modelling
HerausgeberAcoustical Society of America, Proceedings of Meetings on Acoustics, Vol. 19, 030073 (2013)
Erscheinungsjahr2013
Abstract
Porous materials are widely used in noise reduction applications. To minimize the external noise produced by aicraft propeller drives, porous materials are implemented. As a part of the project Sonderforschungsbereich 880 "Fundamentals of High Lift for Future Civil Aircraft", porous surfaces are used in the High-lift configuration to mitigate the flow noise and to influence the structure-borne sound. In order to model the performance of the applied poroelastic material, an approach coupling a poroelastic material with an elastic structure using Finite Element Method is presented. The Biot's theory is used to model the poroelastic material. The aim of this work is to simulate the effect of the entry and transmission of the structure-borne sound into the poroelastic medium. An example of the implemented model shows the plausibility of presented approach.
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Autor(en) Zahid, Muhammad | Beck, Silja | Langer, Sabine
TitelModeling of flow-induced sound in poroelastic materials
Herausgeber5th Biot Conference on Poromechanics (BIOT-5), pp. 882--890, Vienna - Austria, July 10-12, 2013 (Reviewed)
Erscheinungsjahr2013
Abstract
The use of poroelastic materials on the surfaces under flows–part of the Collaborative Research SFB 880, “Fundamentals of high-lift for future commercial aircrafts”– is investigated. Besides the positive influence that porous surfaces have on aeroacoustics, a poroelastic layer may also help reduce the impact sound. An approach to model the interface between a flow and a poroelastic material, which tracks the propagation of flow-induced structure-borne sound into the poroelastic medium, is illustrated. Firstly, the overall simulation approach and the selected material model is presented, followed by an explanation of the coupling conditions for the interface between the fluid and the poroelastic material. To illustrate the plausibility of this coupling, flow-induced structure-borne sound entry into an airfoil-like structure, layered with a porous material, is examined. The analysis is carried out on a finite element method-based in-house code.
Internet Linkhttp://ascelibrary.org/doi/abs/10.1061/9780784412992.106


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Autor(en) Krukow, Ian | Dinkler, Dieter
TitelA Reduced-Order Model for Aeroelastic Studies on Circulation Controlled Wings
HerausgeberGACM, Hamburg
Erscheinungsjahr2013
Abstract
Take-off and landing of commercial aircraft on short runways in urban areas are possible, if noise emission and minimum flight velocity are adjusted accordingly. The loss of lift due to the lower velocity has to be outweighed by active high-lift devices. A possible approach to achieve the necessary increase in lift is the application of the Coanda effect, which is able to avoid flow separation at the trailing edge at high flap angles. With the application of circulation control, the aeroelasticity has to be taken into account, because the deformation of the airfoil may reduce the increase in lift significantly. For numerical simulations of extensive case studies, a reduced-order model is developed, which includes the effect of the Coanda stream on the generation of lift in a parametrised form. The reduced-order model can be integrated into a simplified flight dynamics model. Developing the aeroelastic model, it is necessary to couple the aerodynamics of the wing profile with the structure of the elastic airfoil. The aerodynamic model is derived from numerical simulations of the flow around the profile with the TAU-code. For a broad range of parameters, the quasi-steady flow as well as harmonic oscillations are simulated depending on the angle of attack, the flap angle and the momentum coefficient of the Coanda stream. From these simulations, the aerodynamic coefficients for lift and momentum are identified and described by a polynomial smoothing function, so that a closed mathematical form is obtained. The two-dimensional model is adapted to the three dimensional wing using the strip theory. The structure behaviour is described by means of a full 3-D-discretization with the finite element method and reduced by a modal transformation. The connection between the aerodynamic forces and the structure model is done by projecting the load distribution onto the eigenmodes of the structure. With the modal transformation, the parameters of the full-scale model, e.g. the air speed and the momentum coefficient of the Coanda stream, are preserved as well as the non-linearities in the equations of motion resulting from the non-linear aerodynamic model. Basic applications of the model are exemplified.


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Autor(en)Diekmann, Jobst Henning
TitelTrim Analysis of Nonlinear Flight Dynamics for a Civil Aircraft with Active High-Lift System
Herausgeber62. Deutscher Luft- und Raumfahrtkongress, Stuttgart, 2013
Erscheinungsjahr2013
Abstract
This paper shows recent flight mechanical simulation results of a civil active high-lift aircraft with blown Coandu a flaps. The main focus lies on the trim analysis of the aircraft. To this end the basic structure and core elements of the nonlinear model, describing the dynamic behavior of an aircraft with this specific type of active high-lift system, are presented. The center of gravity location range allowing controllability and static stability of the aircraft is determined, followed by an analysis of the resulting characteristics of the aerodynamic model and their impact on the trim results of the aircraft. The results show specific flight mechanical difficulties due to the active high-lift system, namely characteristics hardly compatible with safe take-off and approach procedures. The physical explanations will be given and discussed. The necessity of the application of a wing leading edge device is pointed out by preliminary studies and further remedial means are proposed.
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Autor(en) Dörbaum, Michael | Juris, Peter | Stübig, Cornelia | Ponick, Bernd
TitelDesign of High-Speed Motors with a High Power Range for Use in Future Aircrafts
HerausgeberPCIM Europe 2013, Nuremberg, Germany
Erscheinungsjahr2013
Abstract
An active air flow control system at the wings of future aircrafts could reduce runway length and increase airport flexibility. In this paper, electrical driven high speed compressor systems for a high power level are investigated. An important design factor is the prevention and dissi- pation of losses inside the machine. Due to the limited installation space and the high power density demand, an appropriate cooling solution must be developed already during the electro- magnetic design phase. Different cooling solutions are examined, which lead to variations in machine size, and their influence on the bending critical speed is discussed. The selection of suitable core material reduces hysteresis and eddy current losses significantly. These losses are calculated with a numerical software taking into account the core characteristics particu- larly for high frequencies. High speed operation makes a prediction of bending critical speeds necessary to provide safe operation.


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Autor(en) Schmitz, Andre | Horst, Peter
TitelBending deformation limits for corrugated morphing skins
Herausgeber19th International Conference on Composite Materials, Montréal, Canada, 2013
Erscheinungsjahr2013
Abstract
Corrugated composites are widely considered as candidates for morphing applications. This presentation extends the understanding of corrugated composites with respect to deformation limits for static bending deformations. For this reason, the curvature at rupture due to layer delamination and fiber fracture of corrugated samples is predicted and compared to appropriate experimental results. Four different sample types are manufactured from unidirectional carbon-fiber/epoxy laminate. Bending experiments are conducted using a specially designed device which subjects the samples to an almost pure state of bending.


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Autor(en) Beutel, Tobias | Schwerter, Martin | Leester-Schädel, Monika | Dietzel, Andreas | Büttgenbach, Stephanus
TitelFlexible Hot-film Anemometer Arrays for Flow Measurements on Curved Structures
HerausgeberProceedings of SPIE 8763 Smart Sensors, Actuators, and MEMS VI, SPIE Microtechnologies, Grenoble, France, 2013
Erscheinungsjahr2013
Abstract
In this paper, a set of flexible aeroMEMS sensor arrays for flow measurements in boundary layers is presented. The sensor principle of these anemometers is based on convective heat transfer from a hot-film into the fluid. All sensors consist of a nickel sensing element and copper tracks. The functional layers are attached either on a ready-made polyimide foil or on a spin-on polyimide layer. These variants are necessary to meet the varying requirements of measurements in different environments. Spin-on technology enables the use of very thin PI layers, being ideal for measurements in transient flows. It is a unique characteristic of the presented arrays that their total thickness can be scaled from 5 to 52 μm. This is essential, because the maximum sensor thickness has to be adapted to the various thicknesses of the boundary layers in different flow experiments. With these sensors we meet the special requirements of a wide range of fluid mechanics. For less critical flow conditions with much thicker boundary layers, thicker sensors might be sufficient and cheaper, so that ready-made foils are perfect for these applications. Since the presented sensors are flexible, they can be attached on curved aerodynamic structures without any geometric mismatches. The entire development, starting from theoretical investigations is described. Further, the micro-fabrication is explained, including all typical processes e.g. photolithography, sputtering and wet-etching. The wet-etching of the sensing element is described precisely, because the resulting final dimensions are critical for the functional characteristics.


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Autor(en) Schwerter, Martin | Beutel, Tobias | Leester-Schädel, Monika | Dietzel, Andreas | Büttgenbach, Stephanus
TitelFlexible Heißfilm-Anemometrie-Arrays zur Strömungsmessung an gekrümmten Strukturen
HerausgeberMikroSystemTechnik Kongress 2013 Proceedings, ISBN 978-3-8007-3555-6, S. 749-752, Aachen
Erscheinungsjahr2013
Abstract
In dieser Arbeit werden der Entwurf, die Herstellung und die Charakterisierung von neuartigen flexiblen AeroMEMS-Heißfilmsensorarrays beschrieben. Als Substrat wird ein Polyimid verwendet, das entweder als fertige Folie vorliegt oder flüssig aufgeschleudert werden kann. Mit letzterem lassen sich Sensorhöhen bis hinab zu 7 μm realisieren. Für die Herstellung der sensitiven Schicht werden zunächst mit verschiedenen Materialien Versuche zur Leitfähigkeit und zum Temperaturkoeffizienten durchgeführt und bewertet, sodass dann ein Sensor mit den gewünschten Eigen-schaften hergestellt werden kann. In der Arbeit wird die vollständige Entwicklung, beginnend bei den theoretischen Überlegungen, bis hin zur mikrotech-nischen Produktion, beschrieben. Dabei wird das nasschemische Ätzen vertieft diskutiert, da es einen besonders kriti-schen Einfluss auf die Eigenschaften des Sensors hat.


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Autor(en) Sommerwerk, Kay | Haupt, Matthias | Horst, Peter
TitelFSI of High Performance High-Lift Devices with Circulation Control via Conditioned Coanda-Jets
HerausgeberProceedings of V Conference on Computational Methods for Coupled Problems in Science and Engineering, June 17-19, Ibiza, Spain
Erscheinungsjahr2013
Abstract
Current transport aircraft are limited to airports with comparatively long runways for take-off and landing. An aircraft with short take-off and landing capabilities is under investigation at the Collaborative Research Center 880. The aircraft employs circulation controlled high lift devices where high velocity air is blown through a slot in front of the flap. These high performance high-lift devices allow take-off and landing of the aircraft at runways of 800 m length. The curved flap leading edge induces a Coanda effect with the jet resulting in an attached flow up to the tip of the flap even at high deflection angles of up to 85°. Examination of the aeroelasticity of the wing is of high importance because of the sensitivity of the Coanda effect to perturbation through deformation and consequential change in flow. The large pressure gradients can play a significant role in the effective use of this jet system. Preliminary studies have shown an influence on aerodynamic performance due to slot deformation. Small changes in the aerodynamic characteristics can have adverse effects on the stall behavior. A flap section model of the wing is used to analyze the performance for several flight states. This high detail model allows capturing fine effects over the whole wing chord and on the slot region while still including wing deformations. The aerodynamic performance of the aeroelastic flap section model is compared to the characteristics of the rigid airfoil. The analyzed flight states give an insight into the influence of the deformation on the flow. Additionally the effects of jet momentum variation on aerodynamics is shown and the dominant stall phenomena presented. The local relative change in pressure can reach values between 10 and 20 % and has an influence on the stall behavior of the section. The change in aerodynamic performance illustrates the influence of small deformations on the sensitive circulation control.


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Autor(en) Burnazzi, Marco | Radespiel, Rolf
TitelSYNERGIES OF SUCTION AND BLOWING FOR ACTIVE HIGH-LIFT FLAPS
HerausgeberDLRK 2013 - German Aerospace Congress 2013, Stuttgart.
Erscheinungsjahr2013
Abstract
The present work represents an advanced step in the multidisciplinary design of an active high-lift system for commercial aircraft. The airfoil configuration developed within the framework of the Collaborative Research Centre SFB880 is composed of an active Coanda flap and a droopnose device. The power required to implement circulation control is provided by electrically-driven compact compressors, positioned along the wing behind the wingbox. This solution could reduce the additional engine power needed for the active high- lift system. Air is provided to the compact compressors by means of a suction slot located on the suction side of the airfoil, which represents an opportunity to increase the aerodynamic performance of the airfoil. The present work investigates the aerodynamic sensitivities of shape and location of the suction slot, in relation to the high-lift performance of the airfoil and to the total pressure recovery achieved at the end of the suction duct. A significant benefit is achieved by suction and the presented analysis yields physical insight into the flow dynamics around the airfoil.
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Autor(en)Keller, Dennis
TitelNumerical Investigation of Engine Effects on the Stability and Controllability of a Transport Aircraft with Circulation Control
HerausgeberAIAA Applied Aerodynamics, San Diego, 2013
Erscheinungsjahr2013
Abstract
The scope of this paper is to illustrate the installation effects of a turboprop engine on a high-lift configuration of a short take off and landing (STOL) aircraft with circulation control. In addition to the influence on the wing performance, the impact on the longitudinal static stability of the whole aircraft is also investigated. Furthermore, critical failure cases, namely one engine inoperative (OEI), as well as an asymmetric circulation control failure are assessed. Therefore, CFD calculations based on the Reynolds-averaged Navier-Stokes (RANS) equations were performed, whereas the propeller is modeled with an actuator disk.


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Autor(en) Sommerwerk, Kay | Haupt, Matthias | Horst, Peter
TitelAeroelastic Performance Assessment of a Wing with Coanda Effect Circulation Control via Fluid-Structure Interaction
HerausgeberAIAA 2013-2791, 31st AIAA Applied Aerodynamics Conference, June 24-27, San Diego, USA
Erscheinungsjahr2013
Abstract
Airports with comparatively long runways are needed for current transport aircraft for takeoff and landing. The necessary runway length as a basic characteristic limits the use of smaller airports with available capacity. An aircraft with short takeoff and landing capabilities is under investigation at the Collaborative Research Center SFB 880. The aircraft employs circulation controlled high lift devices allowing short takeoff and landing. High velocity air is blown through a slot in front of the flaps to interact with the oncoming boundary layer. The curved flap leading edge behind the slot induces a Coanda effect resulting in an attached flow up to the tip of the flap even at high deflection angles of up to 85°. Evaluation of the aeroelasticity of the wing is of high importance due to the sensitivity of the Coanda effect to perturbation through deformation and consequential change in flow. Perturbation sources are the deformation of the slot lip as well as the global wing deflection. High fidelity fluid structure interaction simulation are used to identify the global and local effects of elastic models. A flap sectional model is used to capture the local slot deformation influence, whereas a complete wing model takes the global deformations into account. The slot stiffness has an influence on the aerodynamic performance, depending on the jet momentum. The small global wing deformations for the analyzed wing have a noticeable but small influence on the aerodynamics.
Internet Linkhttp://dx.doi.org/10.2514/6.2013-2791


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Autor(en) Weiss, Tayson | Wolfgang, Heinze | Peter, Horst
TitelInfluence of Propeller Aerodynamics on Structural Wing Box Optimization in Integrated Preliminary Aircraft Desgin
Herausgeber31st AIAA Applied Aerodynamics Conference, San Diego, 2013
Erscheinungsjahr2013
Abstract
The present study evaluates the consideration of propeller slipstream effects in a structural optimization procedure as commonly used in integrated preliminary aircraft design. Therefore an optimization model comprising aerodynamic and structural analysis of an exemplary short range aircraft wing box is developed. The aerodynamic loads are calculated with a potential-based 3D-panel code employing an actuator disk vortex tube and membrane arrangement for reflection of the propeller slipstream influence. Structural analysis is provided by means of a finite element model. The comparison of stress distributions and wing box masses obtained with and without incorporation of the propeller slipstream model indicate a distinct influence of the latter on the optimization result and thus on the entire underlying preliminary aircraft design process.


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Autor(en)Weiss, Tayson
TitelPowered High Lift Aerodynamics in Preliminary Aircraft Design
Herausgeber62. Deutscher Luft- und Raumffahrtkongress, Stuttgart, 2013
Erscheinungsjahr2013
Abstract
An appropriate mapping of jet momentum expenditure and lift gain is prerequisite to the preliminary design of powered high lift aircraft. Due to the complex nature of active high lift flows this mapping is usually found at high computational costs, detrimental to an aircraft design process characterized by a vast design space. This paper presents a procedure allowing for comparatively fast aerodynamic calculation of powered high lift aircraft designs utilizing the Coanda effect. The method relates a 3D potential theory based aerodynamic aircraft model to an airfoil data field obtained by a Reynolds-averaged Navier-Stokes code. The procedure is demonstrated for a high lift configuration of an aircraft equipped with internally blown Coanda flaps. Result comparison with a 3D Reynolds-averaged Navier-Stokes reference model demonstrates the method’s capability to accurately predict global jet momentum, whereas local jet momentum evaluation remains an open challenge.


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Autor(en) Rudenko, Anton | Rose, Michael | Monner, Hans Peter
TitelOptimization Framework for Stiffness and Layout Tailoring of a Morphing High Lift System
Herausgeber6th ECCOMAS Conference on Smart Structures and Materials / Turin 2013
Erscheinungsjahr2013
Abstract
At the Institute of Composite Structures and Adaptive Systems (FA, Prof. Wiedemann) of the DLR a process chain for development of flexible and gapless wing leading edge is being evolved within the framework of the collaborative research centre SFB880. The main topic of the research is to achieve the exceedingly high grade of leading edge morphing which is a key technology for realizing an active blown Coand˘a-flap based high lift system. The overall smart droop nose concept was formed in cooperation with Airbus and EADS, whereby the DLR Institute FA dealt with the design and manufacturing technologies of the morphable composite skin. Due to the fact that the novel high lift system in SFB880 requires considerably more droop (>300%) than achieved before, a new approach based on optimization of the skin and the actuation kinematics in a loop was chosen. An additional feature of the new approach is the application of compliant mechanisms for a beneficial distribution of the skin loads. The content of this paper is formed by the detailed presentation of the framework for topology optimization of a composite skin combined with an actuation kinematics established at the institute FA of the DLR.
Internet Linkhttp://elib.dlr.de/86575/


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Autor(en) Krafczyk, Manfred | Uphoff, Sonja | Schönherr, Martin | Geier, Martin | Kucher, Kostyantyn | Stiebler, Maik
TitelHPC CFD Simulations Based on Kinetic Methods Using Multi- and Many-Core Systems
HerausgeberDevelopments in Parallel, Distributed, Grid and Cloud Computing for Engineering, Chapter 6, 2013, pp. 125-149 (Reviewed)
Erscheinungsjahr2013
Abstract
In recent years it has become obvious that modern computer hardware essentially will rely on multi- and many-core architectures to increase computational performance. Yet, only very few computational frameworks are ready to meet this challenge from an algorithmic and software engineering point of view. This chapter gives an overview about the recent work undertaken by our group in the context of high-performancecomputing (HPC) simulations in the area of computational fluid dynamics (CFD) in civil engineering. We will address different aspects of the simulation pipeline ranging from the efficiency of explicit numerical kernels capable of exploiting modern central processing units (CPU) as well as general purpose graphics processing units (GPGPU) architectures as well as domain-decomposition aspects for local time stepping schemes on Eulerian grids and the importance of hardware aware data structures. Our basic modeling approach for CFD is based on various lattice-Boltzmann models (LBM) tailored for turbulent flows. After a short introduction into the basic methods we will discuss several computational examples of complex flow simulations with up to five billion degrees of freedom. These examples demonstrate the feasibility of LBM for complex flow problems and the efficiency of GPGPU based simulations which allow simulations with more than a billion degrees of freedom (DOF) on desktop systems. Thus kinetic techniques for transport simulation may play a more prominent role in computational engineering due to their intrinsic suitability for present and future multi- and many-core architectures.
Internet Linkhttp://www.ctresources.info/csets/chapter.html?id=514


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Autor(en)Uphoff, Sonja
TitelDevelopment and Validation of turbulence models for Lattice Boltzmann schemes
HerausgeberDissertation, TU Braunschweig
Erscheinungsjahr2013
Abstract
Computational fluid mechanics has become a standard approach in many branches of engineering. Simulation of flow on the building- and infrastructure scale, however, remains very challenging and is mostly restricted to basic research at the present stage. In particular, accurate, three-dimensional, time-resolved simulation such as Large Eddy Simulation is still rarely used despite its potential. On the other hand, it is reasonable to expect a growing influence of these methods as computers become more powerful and numerical methods evolve. In the present work the Lattice Boltzmann method is chosen as a starting point to analyze simulations of flow around buildings. This approach appears to be particularly apt for such applications due to its very good scalability with respect to parallel computing. Different variants of the Lattice Boltzmann method, namely the Lattice Bhatnagar-Gross-Krook (LBGK) method, the Multiple Relaxation Time (MRT) method, and variants of the Cascaded Lattice Boltzmann (CLB) method have been implemented and compared on the basis of standard benchmarks. Furthermore, several turbulence models, such as the Smagorinsky model, the wall adapting local eddy-viscositymodel, and Vreman’s model have been investigated. One focus was on the applicability of the Lattice Boltzmann method to turbulent flows, considering also the interdependence between the numerical method and the LES model. Particular attention was paid to the ability of these models to correctly reproduce turbulent shear flows. Some typical infrastructure elements have been studied and compared to windtunnel data. The simulations were carried out on a PC cluster and on graphics processing chips (GPGPUs). Overall, the Lattice Boltzmann method has yielded good results for turbulent flow simulations, which is documented in several benchmarks. In particular, the results for the FCLB model show for the first time for a reasonably complex benchmark, that themodel performs well for turbulent flows, for which an explanation is attempted.


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Autor(en) Beutel, Tobias | Leester-Schädel, Monika | Dietzel, Andreas
TitelManufacturing of flexible micro hot-film probes for aeronautical purposes
HerausgeberMicroelectronic Engineering, Volume 111, Elsevier, Pages 238–241 (Reviewed)
Erscheinungsjahr2013
Abstract
In this work we present the design, fabrication and characterization of flexible AeroMEMS hot-film probes. The hot-films are fabricated on polyimide foil (PI). The foil is bonded onto a glass or silicon substrate in order to get a rigid structure for using standard silicon bulk-micromachining processes. After micro fabrication is finished the PI foil can be easily removed from the substrate. The foil itself is flexible enough to be placed on complex curved contours typically used in aerodynamic tests. This study discusses the failures introduced by geometry effects which occur due to isotropic wet etching of the metal layers. After these investigations, one hot-film design was chosen to create a sensor array for special measurements of wall shear stress in fluid mechanics. The array consists of 32 hot-film sensors custom made for an aerodynamic test. The properties of the sensing elements are optimized for the measurement set-up, providing a simple implementation. The sensing elements were finally made of Nickel, while the wiring was electroplated with 2 μm of Copper. Using the advantages of both materials is unique. It is assumed that due to the extremely flat design, the sensor including its Cu wiring has no influence on the flow. The foil, including the thin wiring is bendable enough to lead the contacts into the wing, making the electrical connection very convenient.


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Autor(en) Geller, Sebastian | Uphoff, Sonja | Krafczyk, Manfred
TitelTurbulent jet computations based on MRT and Cascaded Lattice Boltzmann models
HerausgeberComputers and Mathematics with Applications, Vol. 65, Iss. 12, 2013, pp. 1956-1966 (Reviewed)
Erscheinungsjahr2013
Abstract
In this contribution a numerical study of a turbulent jet flow is presented. The simulation results of two different variants of the Lattice Boltzmann method (LBM) are compared. The first is the well-established D3Q19 MRT model extended by a Smagorinsky Large Eddy Simulation (LES) model. The second is the D3Q27 Factorized Cascaded Lattice Boltzmann (FCLB) model without any additional explicit turbulence model. For this model no studies of turbulent flow with high resolution on nonuniform grids existed so far. The underlying computational procedure uses a time nested refinement technique and a grid with more than a billion DOF. The simulations were conducted with the parallel multi physics solver VirtualFluids. It is shown that both models are feasible for the present flow case, but the FCLB outperforms the traditional approach in some aspects.
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Autor(en) Uphoff, Sonja | Kucher, Kostyantyn | Krafczyk, Manfred
TitelSimulation of Turbulent Boundary Layer Flow over Porous Media with a Lattice Boltzmann Model
Herausgeber5th GACM Colloquium on Computational Mechanics, Hamburg, 2013
Erscheinungsjahr2013
Abstract
Simulation of Turbulent Boundary Layer Flow over Porous Media with a Lattice Boltzmann Model
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Autor(en) Seume, Jörg | Burnazzi, Marco | Schwerter, Martin | Behr, Christian | Rudenko, Anton | Schmitz, Andre | Dörbaum, Michael | Atalayer, Caglar
TitelSFB 880 – Efficient High Lift
Herausgeber62nd DLRK, Stuttgart, Germany, 2013
Erscheinungsjahr2013
Abstract
The collaborative research center (Sonderforschungsbereich, abbreviated SFB) 880 investigates the fundamentals of high-lift generation for future civil aircraft, focusing on the fields of aeroacoustics, lift generation and flight dynamics. The present paper addresses the research on efficient lift generation which is denoted as Research Area B. The underlying research hypothesis of the present work is that further significant increases in lift generation of civil aircraft compared to the current state technology are possible using active lift systems. The investigated high-lift concept utilizes a combination of internally blown flaps and circulation control to achieve high flow turning over the wing. A flexible leading edge device for the wing without gap or step is designed to reduce noise generation and to increase the efficiency of the active blowing system. Further, closed-loop control of blowing is envisaged. The overall objective of the project is to design an active lift system that requires a minimum of additional engine power to generate the required lift. A multidisciplinary, collaborative approach is taken, combining the fields of aerodynamics, material science, microtechnology, turbomachinery and electrical engineering to obtain optimum performance of the overall lift generation system. The research progress during the first two years of this ongoing work is presented in this paper.
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Autor(en) Horst, Peter | Keller, Dennis | Diekmann, Jobst Henning | Krukow, Ian | Sommerwerk, Kay
TitelSFB880: Flight Dynamics
HerausgeberDeutscher Luft- und Raumfahrtkongress, Stuttgart, 2013
Erscheinungsjahr2013
Abstract
The paper summarizes approaches and first results on flight dynamics of the Collaborative Research Centre SFB 880 - "Fundamentals of High Lift for Future Commercial Aircraft" - , i.e. high fidelity solutions of dynamics in aerodynamics, aeroelasticity and flight control.
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Autor(en)Wiegel, Julian
TitelStudent Assistant - Simulation of Aircraft Noise
HerausgeberThird Symposium on "Simulation of Wing and Nacelle Stall", Braunschweig, Germany, June 2012
Erscheinungsjahr2013
Abstract
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Autor(en) Lippitz, Nicolas | Rösler, Joachim | Hinze, Björn
TitelPotential of Metal Fibre Felts as Passive Absorbers in Absorption Silencers
HerausgeberMetals, ISSN 2075-4701, 3, MDPI AG, 150-158, Basel, Switzerland, 2013 (Reviewed)
Erscheinungsjahr2013
Abstract
The growing noise exposure of residents, due to a rising number of flights, causes significant impacts on physical health. Therefore it is necessary to reduce the noise emission of aircrafts. During take-off, the noise generated by the jet engines is dominating. One way to lower the noise emission of jet engines is to build an absorption silencer by using porous liners. Because of the high thermic and corrosive attacks as well as high fatigue loads, conventional absorbers cannot be used. A promising material is sintered metal fibre felts. This study investigates the suitability of metal fibre felts for the use as absorption material in silencers. The influences of pore morphology, absorption coefficient, determined with perpendicular sound incidence, as well as geometric parameters of the silencer to the damping are identified. To characterise the material, the parameters fibre diameter, porosity and thickness are determined using three-dimensional computer tomography images. The damping potential of absorption silencers is measured using an impedance tube, which was modified for transmission measurements. The essential parameter to describe the acoustic characteristics of porous materials is the flow resistivity. It depends on the size, shape and number of open pores in the material. Finally a connection between pore morphology, flow resistivity of the metal fibre felts and damping potential of the absorption silencer is given.
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Internet Linkhttp://www.mdpi.com/2075-4701/3/1/150/pdf


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Autor(en) Rurkowska, Katherina | Sabine, Langer
TitelPrediction of acoustic behaviour of microperforated plates in High-lift configuration
HerausgeberAIA-DAGA, Meran
Erscheinungsjahr2013
Abstract
Porous materials are widely used in noise reduction applications. To minimize the external noise produced by aicraft propeller drives, microperforated plates are implemented. As a part of the project Sonderforschungsbereich 880 "Fundamentals of High Lift for Future Civil Aircraft", porous surfaces are used in the High-lift configuration to mitigate the flow noise and influence the structure-borne sound. In order to model the performance of the these microperforated plates, an approach based in the Johson-Allard for ridig frame porous media proposed by Atalla and Sgard is used. In this model an equivalent tortuosity is used and Biots parameters for cylindrical pores are assumed. The aim of this work is to predict the behavior and acoustic effect of the used microperforated plates during its operation lifetime. The sound absorption of the porous materials is carried on with our in-house Code using the transfermatrix method.
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Autor(en) Teichel, Sönke | Verstraete, Tom | Seume, Jörg
TitelOptimized preliminary design of compact axial compressors: A comparison of two design tools.
Herausgeber31st AIAA Applied Aerodynamics Conference, San Diego, 2013
Erscheinungsjahr2013
Abstract
The resulting designs of two di erent preliminary design tools which are combined with an automatic optimization process are compared. The basis of comparison is the design task of a single-stage axial compressor with design mass ow rate of 2.3 kg/s and the goal to achieve high total pressure ratios. Although di erent design approaches are applied the two design processes result in similar compressor designs. The compressor designs are characterized by high reaction and low aspect ratio of the blades. The performance of the designs, as predicted by the preliminary design tools, is con rmed with CFD simulations with acceptable margin of deviation. Both optimized preliminary design processes provide designs that are a good basis for further detailed design.


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Autor(en) Krukow, Ian | Dinkler, Dieter | Haupt, Matthias
TitelEntwicklung eines reduzierten Modells für die Beurteilung der Aeroelastik eines Tragflügels mit aktivem Hochauftriebssystem
Herausgeber61. Deutscher Luft- und Raumfahrtkongress, Berlin
Erscheinungsjahr2012
Abstract
Mit dem Einsatz aktiver Zirkulationskontrollen ist eine im Einzelfall erhebliche Verkürzung der Start- und Landebahnlängen von modernen Flugzeugen möglich. Im vorliegenden Aufsatz soll der Einfluss der Zirkulationskontrolle auf das aeroelastische Verhalten einer Flugzeugtragfläche untersucht werden. Für die numerische Analyse wird ein vereinfachendes Berechnungsmodell vorgestellt, mit dem systematische Parametervariationen möglich sind. Grundlage des Modells ist die Modellreduktion mit Hilfe der Modal-Analyse, sodass eine effiziente Durchführung numerischer Studien sowie die Berücksichtigung der Aeroelastik in einem weiterführenden flugmechanischen Modell möglich ist.


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Autor(en) Krukow, Ian | Dinkler, Dieter | Haupt, Matthias
TitelModellreduktion für die Aeroelastik eines Flügels mit aktivem Hochauftriebssystem
Herausgeber61. Deutscher Luft- und Raumfahrtkongress, Berlin
Erscheinungsjahr2012
Abstract
Mit dem Einsatz aktiver Zirkulationskontrollen ist eine im Einzelfall erhebliche Verkürzung der Start- und Landebahnlängen von modernen Flugzeugen möglich. In der vorliegenden Arbeit soll der Einfluss der Zirkulationskontrolle auf das aeroelastische Verhalten einer Flugzeugtragfläche untersucht werden. Für die numerische Analyse wird ein vereinfachendes Berechnungsmodell vorgestellt, mit dem systematische Parametervariationen möglich sind. Grundlage des Modells ist die Modellreduktion mit Hilfe der Modal-Analyse, sodass eine effiziente Durchführung numerischer Studien sowie die Berücksichtigung der Aeroelastik in einem weiterführenden flugmechanischen Modell möglich ist. Das Poster gibt einen Überblick über die entwickelten Modelle und deren Ergebnisse. Eine ausführliche Darstellung ist im zugehörigen Konferenzartikel zu finden.


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Autor(en)Sinapius, Gerrit
TitelKompakte dynamische Kompressoren - Ergänzende Untersuchungen zur Verdichterbauart Diagonalverdichter zu SFB 880 - B4
HerausgeberISM
Erscheinungsjahr2012
Abstract
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Autor(en) Sommerwerk, Kay | Haupt, Matthias
TitelStructural Sizing of a CFRP Wing with Coanda Flaps via CFD-CSM Coupling
HerausgeberProceedings of 61. Deutscher Luft- und Raumfahrtkongress, Berlin
Erscheinungsjahr2012
Abstract
Preliminary aircraft design suffers from the lack of detailed models to verify the assumed parameters of loads and structures, which may have a high impact on the accuracy of the solutions. A 100 PAX commercial aircraft with short take-off and landing capabilities of 800 meters with circulation controlled high lift devices is under investigation at the Collaborative Research Centre SFB 880. High velocity air is blown through a slot in front of the high lift device thus inducing a Coanda effect on the curved flap leading edge. This leads to an attached flow at high flap angles inducing very high lift coefficients. In this paper, a global wing analysis is conducted and the results are compared with preliminary extrapolations. Several designs for the air feed system integration are proposed and examined regarding weight and stiffness characteristics on a representative high lift device section model. Fluid structure coupling is employed during the analyses to transfer aerodynamic loads and structural displacements to determine the aero-elastic impact of the slot stiffness on the Coanda effect during landing. The attained aerodynamic performance results and structural characteristics of each configuration are compared and the advantages discussed.


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Autor(en) Werner-Spatz, Christian | Heinze, Wolfgang | Horst, Peter | Radespiel, Rolf
TitelMultidisciplinary conceptual design for aircraft with circulation control high-lift systems
HerausgeberCEAS Aeronautical Journal, Volume 3,Issue 2-4, Springer-Verlag, pp 145-164 (Reviewed)
Erscheinungsjahr2012
Abstract
Active high-lift technologies have often proven their potential in aerodynamic analyses and wind tunnel tests, but have so far played only a minute role in civil production aircraft. This is expected to change in the future only if such technologies can be accounted for early in the aircraft design process. In this paper, the adaptation of a conceptual design process is presented, enabling it to consider circulation control as a high-lift technology. It is shown that the main aerodynamic effects of a blown flap in the boundary layer control regime can be satisfactorily modeled with a potential theory method. Some sample results of the design process indicate a potential for significant reductions of required field length in comparison with today’s aircraft, creating the potential to increase the capacity of the air transportation system, without increasing overall aircraft mass or direct operating cost.
Internet Linkhttp://link.springer.com/article/10.1007/s13272-012-0049-5


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Autor(en) Klesa, Jan | Langer, Sabine
TitelEinfluss von Verschmutzung auf die Absorptionswirkung von porösen Materialien
HerausgeberProceedings of DAGA 2012, Deutsche Gesellschaft für Akustik e. V. (DEGA)
Erscheinungsjahr2012
Abstract
Poröse Oberflächen haben positive akustische Eigenschaften und werden in verschiedenen technischen Anwendungen verwendet. Im Zuge des Gebrauchs bzw. des technischen Einsatzes und im Laufe ihrer Lebensdauer werden diese Materialien häufig verschmutzt, was sich auch nachteilig auf die akustischen Eigenschaften auswirken kann.
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Autor(en) Hinze, Björn | Rösler, Joachim
TitelCharacterization of Open-Pored Metals Using Image Processing
HerausgeberCharacterization of Minerals, Metals and Materials (eds J.-Y. Hwang, S.N. Monteiro, C.-G. Bai, J. Carpenter, M. Cai, D. Firrao and B.-G. Kim), ISBN 9781118371305, John Wiley & Sons, Inc., 185-192, Hoboken, NJ, USA, 2012 (Reviewed)
Erscheinungsjahr2012
Abstract
The most important characteristic of open-pored metals is porosity, since it enables all of their functional applications as filters or sound absorbers. Due to the notch effect of the pores, mechanical properties of porous metals are better than the ones of comparable structures made of polymers or ceramics. Consequently, only open-pored metals can be used in aircrafts to reduce flow noise or noise resulting from the core engine by acoustic absorption. Absorption properties depend highly on pore size and porosity of the material, which must be characterized as precisely as possible in order to analyze the correlation between morphology and noise reduction performance. Here, a line segmenting method is explained in order to characterize pore size and porosity of absorber materials using image processing based on two dimensional microscopy images, including sample preparation and specification of the set-up. Then, the influence of the pore structure on the measured absorption behavior is discussed. Finally, the correlation of acoustic behavior, pore morphology, and porosity is outlined.
Internet Linkhttp://onlinelibrary.wiley.com/doi/10.1002/9781118371305.ch23/summary


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Autor(en) Hinze, Björn | Rösler, Joachim | Lippitz, Nicolas
TitelNoise Reduction Potential of Cellular Metals
HerausgeberMetals, ISSN 2075-4701, 2, MDPI AG, 195-201, Basel, Switzerland, 2012 (Reviewed)
Erscheinungsjahr2012
Abstract
Rising numbers of flights and aircrafts cause increasing aircraft noise, resulting in the development of various approaches to change this trend. One approach is the application of metallic liners in the hot gas path of aero-engines. At temperatures of up to 600 °C only metallic or ceramic structures can be used. Due to fatigue loading and the notch effect of the pores, mechanical properties of porous metals are superior to the ones of ceramic structures. Consequently, cellular metals like metallic foams, sintered metals, or sintered metal felts are most promising materials. However, acoustic absorption depends highly on pore morphology and porosity. Therefore, both parameters must be characterized precisely to analyze the correlation between morphology and noise reduction performance. The objective of this study is to analyze the relationship between pore morphology and acoustic absorption performance. The absorber materials are characterized using image processing based on two dimensional microscopy images. The sound absorption properties are measured using an impedance tube. Finally, the correlation of acoustic behavior, pore morphology, and porosity is outlined.
Internet Linkhttp://www.mdpi.com/2075-4701/2/2/195/pdf


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Autor(en) Beutel, Tobias | Leester-Schädel, Monika | Dietzel, Andreas
TitelDesign and Manufacturing of Flexible Micro Hot Film Probes for Aeronautical Purposes
HerausgeberMikro- and Nanoengineering, Toulouse, Frankreich
Erscheinungsjahr2012
Abstract
In this work the design, fabrication and characterization of flexible AeroMEMS hot-film probes is presented. The sensor principle is based on heat transfer from an electrically heated hot-film into the flow. The power consumed is in relation to the flow [1]. In this new approach the hot films are fabricated on Polyimid foil (PI). The foil is bonded onto a glass or silicon substrate in order to get a rigid structure for using standard silicon bulk-micromachining processes. After micro fabrication is finished the PI foil can be easily removed from the substrate. The foil itself is flexible enough to be placed on complex curved contours typically used in aerodynamic tests.
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Autor(en)Diekmann, Jobst Henning
TitelInvestigation of Flight Dynamics of a Civil Aircraft with Active High Lift System
HerausgeberDeutscher Luft- und Raumfahrtkongress 2012 (Berlin)
Erscheinungsjahr2012
Abstract
In this paper ongoing research on the flight dynamic modeling and analysis of an aircraft with active high lift is presented. The considered aircraft is being designed with an aircraft multidisciplinary design and optimization tool (PrADO) and is a twin turboprop equipped with an active high lift system consisting of a Coandă surface flap whose knee is blown to enable boundary layer control. In this paper, a longitudinal model is derived from the first aerodynamic data available for this aircraft and used to make a first assessment of the flight dynamics of this aircraft configuration. In particular, the effects of the active high lift system on the trim conditions and the normal modes of the aircraft are shown, as well as a first assessment of the consequences of an active blowing system failure. A remarkable intermediate result is that with proper actions of the pilot (or the flight control system) such a failure seems to have significantly less severe consequences than initially feared.
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Autor(en) Müller, Lars | Kozulovic, Dragan | Hepperle, Martin | Radespiel, Rolf
TitelInstallation Effects of a Propeller Over a Wing with Internally Blown Flaps
HerausgeberProc. of the 30th AIAA Applied Aerodynamics Conference, No. AIAA 2012-3335, New Orleans, LA (USA)
Erscheinungsjahr2012
Abstract
Aiming at maximum climb performance, the lift-to-drag ratio and the installed thrust of a STOL transport aircraft can be enhanced through a synergistic propeller integration. Reynolds- Averaged-Navier-Stokes simulations have been conducted on a generic geometry to quantify the aerodynamic interactions between the propulsion system and a wing with blown flaps. At takeo , a conventional tractor configuration shows a distinct thrust vectoring e ect inducing large lift and drag increments. By relocating the propeller at midchord above the wing, the lift over drag ratio and the installed eciency are considerably improved while losing half of the lift augmentation. Compared to a simple over-the-wing installation, a channel wing design with a partially embedded propeller has the advantage that the thrust vector is closer to the center of gravity resulting in a smaller pitching moment due to thrust. An issue of over-the-wing propellers is the inhomogeneous inflow to the propeller which leads to cyclic variations in blade load and reduced net thrust.
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Autor(en) Müller, Lars | Kozulovic, Dragan | Hepperle, Martin | Radespiel, Rolf
TitelThe Influence of the Propeller Position on the Aerodynamics of a Channel Wing
HerausgeberProc. of 61. Deutscher Luft- und Raumfahrtkongress, No. DLRK 2012-281259, Berlin (Germany)
Erscheinungsjahr2012
Abstract
The paper investigates a generic channel wing configuration regarding the aerodynamic sensitivities to design parameters. Numerical simulations include a variation of the channel depth, the chordwise position of the propeller and clearance for the simplified wing and actuator disk geometry. Evaluation of the lift-to-drag ratio of the wing and the propeller efficiency indicate complex dependencies between geometric parameters and aerodynamic performance. It is evident that a highly integrated design with large embedding depth and minimum gap size leads to most beneficial influences on the wing but an adverse effect on the propeller. As the propulsion system always suffers from this kind of installation, the mutual influence is not of synergistic nature. Evaluating a corrected lift-to-drag ratio which takes the thrust loss on the actuator disk into account, the figure of merit of the overall configuration is only little affected by the three design parameters. More specifically, a less close coupling is considered advantageous when aiming at high climb angles. Together with the expected shielding capabilities, a small noise footprint at take-off can be indirectly achieved through aerodynamically driven measures.
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Autor(en) Beutel, Tobias | Ferreira, Nelson | Leester-Schädel, Monika | Büttgenbach, Stephanus
TitelRobust pressure sensor for measurements in boundary layers of liquid fluids with medium total pressures
HerausgeberSPIE Microtechnologies, Proc. of SPIE Vol. 8066, Prague, Czech Republic, 80661U1-11
Erscheinungsjahr2011
Abstract
In this work, the latest results of the design, fabrication and characterization of a new MEMS piezoresistive pressure sensor are presented. It is made of silicon using a boron diffusion process to create piezoresistors. Significant changes in the layout as well as in the micro-fabrication process have been made, e.g. anodic bonding of a Pyrex cover on the backside. These lead to a very precise pressure sensor, which is tailor made for high dynamic measurements in fluids with a total pressure up to 4 bar. This new piezoresistive pressure sensor has been developed in order to meet the special requirements of measurements in fluid mechanics, particularly with regard to the non-intrusive nature of the sensor. The sensor development, starting with the simulation of mechanical stresses within the diaphragm is described. These calculations have lead to an optimized placement of the piezoresistors in order to achieve a maximum sensitivity. The result of this work is a sensor which has well known properties. Important parameters including sensitivity, resonance frequency and maximum load are described precisely. These are necessary to enable new measurements in the boundary layer of fluids. The experiments and the initial results, e.g. its linearity and its dynamic capability are demonstrated in several figures.
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Internet Linkhttp://dx.doi.org/10.1117/12.885610


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Autor(en) Beutel, Tobias | Leester-Schädel, Monika | Büttgenbach, Stephanus
TitelDesign and evaluation process of a robust pressure sensor for measurements in boundary layers of liquid fluids
HerausgeberMicrosystem Technologies (ISSN 0946-7076), Volume 18, Issue 7 (2012), Springer Verlag, pp. 893-903 (Reviewed)
Erscheinungsjahr2011
Abstract
In this work, the latest results of the design, fabrication and characterization of a new MEMS piezoresistive pressure sensor are presented. Significant changes in the layout as well as in the micro-fabrication process have been made, e.g. anodic bonding of a glass cover on the backside. The sensor has been developed in order to meet the special requirements of measurements in fluid mechanics, particularly with regard to the non-intrusive nature of the sensor. The sensor development, starting with the simulation of mechanical stresses within the diaphragm resulting from a pressure of up to 4 bar is described. These calculations have lead to an optimized placement of the piezoresistors in order to achieve a maximum sensitivity. Important parameters including sensitivity, resonance frequency and maximum load are described precisely. The experiments and the initial results, e.g. its linearity and its dynamic capability are demonstrated.
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Internet Linkhttp://dx.doi.org/10.1007/s00542-011-1404-x


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Autor(en) Schönherr, Martin | Kucher, Kostyantyn | Geier, Martin | Stiebler, Maik | Freudiger, Sören | Krafczyk, Manfred
TitelMulti-thread implementations of the lattice Boltzmann method on non-uniform grids for CPUs and GPUs
HerausgeberComputers and Mathematics with Applications, Vol. 61, 12, 2011, pp. 3730-3743 (Reviewed)
Erscheinungsjahr2011
Abstract
Two multi-thread based parallel implementations of the lattice Boltzmann method for nonuniform grids on different hardware platforms are compared in this paper: a multi-core CPU implementation and an implementation on General Purpose Graphics Processing Units (GPGPU). Both codes employ second order accurate compact interpolation at the interfaces, coupling grids of different resolutions. Since the compact interpolation technique is both simple and accurate, it produces almost no computational overhead as compared to the lattice Boltzmann method for uniform grids in terms of node updates per second. To the best of our knowledge, the current paper presents the first study on multi-core parallelization of the lattice Boltzmann method with inhomogeneous grid spacing and nested time stepping for both CPUs and GPUs.
Internet Linkhttp://www.sciencedirect.com/science/article/pii/S0898122111002999#


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Autor(en) Ahrenholz, Benjamin | Niessner, Jennifer | Helmig, Rainer | Krafczyk, Manfred
TitelPore-scale determination of parameters for macroscale modeling of evaporation processes in porous media
HerausgeberWater Resour. Res., 47, W07543, doi:10.1029/2010WR009519, 2011 (Reviewed)
Erscheinungsjahr2011
Abstract
Evaporation is an important process in many natural and technical systems, such as the unsaturated zone of the subsurface or microchannel evaporators. For the understanding and prediction of the involved processes, numerical simulations of multiphase flow and transport processes are an important tool. In order to achieve an accurate, physically based description of kinetic interphase mass and heat transfer occurring during evaporation, the numerical model has to account for the interfacial areas between phases. A recently developed model for two-phase flow in porous media is able to account for the involved processes by using interfacial areas explicitly as parameters in the model. The crucial issue, however, is the determination of the relationships between specific interfacial areas, capillary pressure, and saturation in this paper, we present a multiphase lattice Boltzmann model, which allows us to determine these relationships. On the basis of the scanned geometry of a natural porous medium, the relationships between specific interfacial areas, capillary pressure, and saturation are determined. To the best of our knowledge, this is the first time that fluid-solid specific interfacial area relationships have been obtained from 19 pore-scale data. Using these functions, we present the results of macroscale simulations of an evaporator device and of drying in a porous medium.
Internet Linkhttp://onlinelibrary.wiley.com/doi/10.1029/2010WR009519/abstract


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Autor(en) Beutel, Tobias | Boese, Christoph | Luzemann, Christoph | Holle, Ansgar | Leester-Schädel, Monika | Büttgenbach, Stephanus
TitelCharacteristics of micro hot-film probes for aeronautical purposes
HerausgeberISMTII 2011, Daejeon, South Korea
Erscheinungsjahr2011
Abstract
In this work we present the design, fabrication and characterization of AeroMEMS hot-film probes. The hot-films are structured on glass or silicon substrates using silicon bulk-micromachining processes. For the initial tests, different metal layers e.g. gold, aluminum, titanium and nickel are magnetron sputtered onto wafer substrates. These hot-films have a variety of geometries and are developed for special measurements of wall-shear stress in fluid mechanics. This study discusses the failures introduced by geometry effects which occur due to isotropic wet etching of the metal layers. Also presented are the non-dynamic and dynamic test procedures used to characterize the hot-film probes. It was discovered that by varying the length and the material, varying electrical properties can be obtained. The determined material constants vary from those known from the bulk material. Dynamic tests in the desktop wind tunnel are also described and the measurement of the heat conduction from the hot-film through the substrate and its influence on the maximum operating frequency is discussed. In the long-term view, hot-films in combination with a pressure sensor on the same chip should be able to detect the state of the flow (laminar or turbulent).
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Autor(en) Hinze, Björn | Rösler, Joachim | Schmitz, Fabian
TitelProduction of nanoporous superalloy membranes by load-free coarsening of gamma'-precipitates
HerausgeberActa Mater., ISSN 1359-6454, 59, Elsevier, 3049-3060, 2011 (Reviewed)
Erscheinungsjahr2011
Abstract
Nickel-based superalloys are predominantly used as structural materials in high-temperature applications due to their exceptional high-temperature strength based on precipitation hardening by the coherent gamma'-phase. In modern superalloys, the gamma'-phase fraction can amount to 75%, at which gamma'-precipitates align as cubes parallel to the <001> directions of the crystal lattice. At high temperatures and under a mechanical load, e.g. during service in gas turbines, the gamma'-cubes coalesce to gamma'-rafts, generating an interpenetrating microstructure of gamma and gamma'. By extracting one phase of this interpenetrated network, nanoporous superalloy membranes containing channel-like interconnected pores are produced. So far, this can only be achieved by applying simultaneously thermal and mechanical loads during tensile creep deformation. Here, a new production process is presented. Due to internal stresses, load-free aging of single-crystalline superalloys, e.g. CMSX-4, also generates an interpenetrating microstructure of gamma and gamma'. This can be utilized to manufacture nanoporous superalloy membranes in the absence of an external mechanical load. The advantage of this process is its simplicity and the potential to fabricate larger membranes than possible by the costly tensile creep deformation process currently used.
Internet Linkhttp://www.sciencedirect.com/science/article/pii/S1359645411000619/pdfft?md5=055defca8b827e098f64c4fa917c591d&pid=1-s2.0-S1359645411000619-main.pdf


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Autor(en) Schwarz, Carsten | Hahn, Klaus-Uwe
TitelAutomated pilot assistance for wake vortex encounters
HerausgeberAerospace Science and Technology, ISSN 1270-9638, Vol. 15, Iss. 5, Elsevier, P. 416 - 421, 2011 (Reviewed)
Erscheinungsjahr2011
Abstract
Wake vortices pose a possible hazard for encountering aircraft in all phases of flight. Hence wake vortex encounters are to be avoided in any case. In case of an unintended wake vortex encounter special aircraft controllers can act as a safety net. Such an active wake vortex control system is being developed by the DLR Institute of Flight Systems based on feed-forward disturbance compensation. The control system has been tested with offline and pilot-in-the-loop investigations as well as with flight tests. It can be shown that the aircraft response can be improved significantly if the pilots are supported by an automatic wake assistance system. For the subjective assessment of the wake vortex encounters a dedicated pilot rating scale has been developed. The results show a clear tendency that the wake vortex controller improves the situation.
Internet Linkhttp://dx.doi.org/10.1016/j.ast.2010.09.008


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Autor(en) Beutel, Tobias | Leester-Schädel, Monika | Wierach, Peter | Sinapius, Michael | Büttgenbach, Stephanus
TitelNovel Pressure Sensor for Aerospace Purposes
HerausgeberSensors & Transducers Journal (ISSN 1726-5479), Vol.115, Issue 4, pp. 11-19 (Reviewed)
Erscheinungsjahr2011
Abstract
In this work, a novel silicon-based sensor for pressure and flow measurements is presented. To meet the special requirements of the aerospace industry a new piezoresistive pressure sensor with a flat surface has been developed, so that the flow is not affected by the sensor. To avoid bonding-wires on top of the sensor a special through-wafer connection is presented. By making other significant changes in the layout as well as in the micro fabrication process, a novel sensor has been created. It is robust enough to be laminated in fibre material, which opens new possibilities for measurements. With this sensor it is possible to characterize the condition of the flow near the separation point. This article describes the complete process from the development to the laminated sensor. Copyright © 2009 IFSA.
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Internet Linkhttp://www.sensorsportal.com/HTML/DIGEST/april_2010/P_595.pdf


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Autor(en) Beutel, Tobias | Boese, Christoph | Büttgenbach, Stephanus
TitelAnalysis of a closed Wheatstone bridge consisting of doped piezo resistors
HerausgeberISMTII 2011, Daejeon, South Korea
Erscheinungsjahr2011
Abstract
In this paper, we present a method to calculate all four resistor values in order to balance a closed Wheatstone bridge. The Wheatstone bridge is an often used circuit for pressure or force measurements, where the applied bridge voltage is constant and the output voltage between the two midpoints is proportional to the measured load. For precise measurements, it is important to have an exactly balanced bridge. Balancing the bridge after the manufacturing process is only possible when the resistors’ exact values are known. Unfortunately it is not possible to measure each single resistor because the other resistors are connected in parallel. An analytic system is presented, which provides the possibility to calculate each resistor by measuring equivalent resistances between the corner points. Our method is unique because it provides a solution where all four resistance values are unknown. All other systems of equations found in literature need at least one known value. Another advantage is the simple realization of an automated measuring system. In this article the method for analyzing a micro pressure sensor that has been developed in recent years at the IMT will be presented. Using this example, we will also describe the measurement principle and the entire micro fabrication process. Subsequently, we will discuss the challenge of the resistance measurement and the corresponding analysis of the Wheatstone bridge. Our system of equations for the exact calculation of each resistor will be derived from the original Wheatstone bridge equations. Finally we will make suggestions to manipulate the conducting paths of every single bridge on a wafer.
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Autor(en) Beutel, Tobias | Niesel, Thalke | Leester-Schädel, Monika | Paces, Pavel | Büttgenbach, Stephanus
Titel5-hole Probe with Integrated Sensing Devices for Measurement of High Frequency Pressure Fluctuations
HerausgeberMikrosystemtechnik-Kongress, Darmstadt, Germany
Erscheinungsjahr2011
Abstract
In the presented application, multiple differential pressure sensors based on bulk micromachining of silicon are used to enable fluid measurements with a five-hole probe. The sensor’s design has been derived from a 3D micro force sensor enabling the measurement of differential pressures in a range of 100 Pa to 120 kPa. The sensors use the piezoresistive effect of doped silicon. The major challenge is the reversibility of the sensors and the linearity of the measurement sig-nals. During the development of the mechanical, electrical and pneumatic subsystems the focus was on reducing the tube’s length. The sensors were therefore placed close to the probe’s head within the mounting pipe, enabling a tube length of only several centimetres. Damping is reduced significantly so that high frequency pressure fluctuations can be detected. With this information the angle of attack (AOA) and the sideslip angle (SSA) can be obtained. The system can be used as a sensing element in an Air Data Computer (ADC) to predict stalling of an airplane, thereby increasing air traffic safety.
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Autor(en) Beutel, Tobias | Holle, Ansgar | Leester-Schädel, Monika | Büttgenbach, Stephanus
TitelAnalysis of a combination of a hot-film and piezo-resistive pressure sensor on a single chip
HerausgeberMikrosystemtechnik-Kongress, Darmstadt, Germany
Erscheinungsjahr2011
Abstract
An integrated wall shear stress sensor was developed at the Institute for Microtechnology (IMT) for novel measurement of flow profiles. The sensor consists of a hot film component, which is fabricated on a single chip together with a sili-con-based pressure sensor. Pressure measurement is realized by the use of piezoresistors, which are structured on a sili-con membrane. They are analyzed to detect a possible temperature drift. The wall shear stress is detected with a hot film, whose heat distribution on the silicon chip was investigated. Several varieties of thermal insulation between the hot film and the piezoresistors were tested, including negative tone epoxy-based photo resist (SU-8) filled cavities.
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Autor(en) Beutel, Tobias | Leester-Schädel, Monika | Wierach, Peter | Sinapius, Michael | Büttgenbach, Stephanus
TitelNovel Pressure Sensor for Aerospace Purposes
HerausgeberInternational Frequency Sensor Association
Erscheinungsjahr2010
Abstract
In this work, a novel silicon-based sensor for pressure and flow measurements is presented. To meet the special requirements of the aerospace industry a new piezoresistive pressure sensor with a flat surface has been developed, so that the flow is not affected by the sensor. To avoid bonding-wires on top of the sensor a special through-wafer connection is presented. By making other significant changes in the layout as well as in the micro fabrication process, a novel sensor has been created. It is robust enough to be laminated in fibre material, which opens new possibilities for measurements. With this sensor it is possible to characterize the condition of the flow near the separation point. This article describes the complete process from the development to the laminated sensor. Copyright © 2009 IFSA.
Internet Linkhttps://sfb880.tu-braunschweig.de/index.php/upload-publikation



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