Numerical Simulations

Numerical Simulations

Few problems in fluid mechanics can be addressed with experiments alone. In many cases, for example, three-dimensional information about the flow field is of interest, which is intricate to access in experiments. In other cases, even the design of an experiment requires detailed knowledge about the flow field.


In such cases it is useful to accompany the experiments with numerical simulations. This allows a precise design of the experiment, a detailed comparison and a mutual validation. Both, experiment and numerical simulation are subject to certain assumptions, limitations and boundary conditions, which can often only be revealed by a mutual comparison.

LES-Simulation eines Profiles mit einem Zackenband zur Transitionsfixierung
At low Reynolds numbers, airfoils are prone to laminar separation bubbles, which usually generates a large drag. Turbulence can be generated in the boundary layer by a zigzag-tape, thus laminar separation can be prevented. The thickness of the zigzag-tape must be chosen carefully, because a tape that is too thick will itself generate a large drag. To develop accurate estimations, the details of artificially forced laminar-turbulent transition must be understood.
Adjoint Elbow
The optimization of flow bodies is usually very complex due to the extremely large number of degrees of freedom. Adjoint methods offer an approach to a very efficient optimization. In this case, the pressure drop of a 90° pipe elbow was minimized by numerically solving the adjoint equations.

We work with the flow solvers of the OpenFOAM package and with the CFD-toolboxes of DLR. We are capable to do all steps in the CFD-chain, from model preparation (CAD), meshing, pre-processing, computation control to post-processing, analysis and data mining.

DES-Simulation airbag inflator
Visualization of the flow field in the vicinity of an airbag cold gas inflator immediately after ignition. The helium discharges with supersonic velocity and forms a so-called "barrel-shock", which is highly unsteady. The buildup of the full flow takes about 0.5 milliseconds.

Selected References

J. ZHANG, L. FOHLMEISTER, P. SCHOLZ, Large-Eddy Simulation of Boundary-Layer Transition over a Zigzag Trip. AIAA Journal (2023). https://arc.aiaa.org/doi/10.2514/1.J062237

SCHNORR, E., SCHOLZ, P., RADESPIEL, R. A method to quantify the supersonic discharge of airbag cold gas inflators. Experiments in Fluids 63, 177 (2022). https://doi.org/10.1007/s00348-022-03521-7 (OpenAccess)

SCHOLZ, P., FRANCOIS, D.G., HAUBOLD, S., SHAOWEI, S., EILTS, P., WM-LES Simulation of a generic intake port geometry, SAE Journal of Engines, Vol. 11, Nr. 3, 2018, doi: 10.4271/03-11-03-0023

PLACZEK, R., SCHOLZ, P., Flow Field Analysis of a Detailed Road Vehicle Model based on Numerical Data, In: Dillmann, A. et al. (Eds), Notes on Numerical Fluid Mechanics and Multidisciplinary Design X, Volume 132, S. 433-442, 2016, doi: 10.1007/978-3-319-27279-5

MAHMOOD, S., SCHOLZ, P., RADESPIEL, R., Numerical Design of Leading Edge Flow Control over Swept High-Lift Airfoil, Aerotecnica Missili & Spazio, The Journal of Aerospace Science, Technology and Systems, Vol. 92, No. 1/2, 2013