Surface Coupled Multi-Field Physics


The investigation of landslides into water involves the interaction of liquefied soil material, water and surrounding air.

Example: Movements of slipping soil

The soil material is modeled as a viscoplastic fluid. The picture above shows the strong interaction between the liquefied soil and the water when the soil impacts on the free water surface.


The hydrodynamic loading and the elastic deformations of water wheels are mutually dependent on each other. A coupled analysis is necessary in order to capture phenomena in fluid and structural domain respectively like eddy shedding and vibrational excitation. This provides the basis for optimising the efficiency of the water wheel construction.

The coupled three field system consisting of rotating structure, surrounding air and streaming water is described as a hydroelastic system using a level set function. Thereby, the level set function indicates the signed shortest distance to the interface between air and water. Both fluid domains are modeled via the incompressible Navier-Stokes equations in a velocity pressure formulation with material parameters described via a regularised Heaviside function. Hence, air and water are modelled uniformly as a single fluid with material parameters changing significantly in the vicinity of the interface. The discretisation takes place using space time finite elements in combination with the shear-slip mesh-update method which takes into account the geometrical and topological changes in the fluid domain.

Example: Experimental model of water wheel SWR-8

[Translate to English:] Simulation des Wasserrades

The instationary flow field surrounding a water wheel structure rotating with a prescribed constant angular velocity is depicted in the figure above.

Silo Discharge

During an excentric discharge of a silo filled with granular material the thin-walled silo-shell is loaded assymmetrically. An excentric discharge is forced by an excentric discharge opening favouring the development of a flow channel due to consolidated material at rest in dead zones. If the thin-walled silo-shell is only designed for symmetric loading it may lose stability if high pressure interacts in the transition zone between flowing granular material and material at rest so that the structural safety is endangered.

The thin-walled silo-shell is modeled in a continuum approach as an elastic-viscoplastic solid material considering large rotations, whereas the flowing granular material is described by a model for viscoplastic compressible fluids by means of the Navier-Stokes equations. The level-set method is used to describe the motion of the free surface during discharge. Between the granular material and the silo-shell advanced slip boundary conditions including friction are taken into account.

With the overall model the impact of shell deformations on the current flow conditions inside the granular material can be analyzed.

Example: Excentric discharge

Entleerung des Silos

The development of an excentric flow channel in a silo with excentric discharge opening is illustrated above. The pressure state along the silo wall is displayed for a cohesive granular material with an angle of internal friction of 20 degree for several instants of time.

Beanspruchung der Siloschale

At initial state the displacements and the effective stresses inside the silo-shell caused by the interacting normal- and shear stress along the silo wall is displayed.

Current Research Projects

  • S. Reinstädler: Modellierung und numerische Simulation von Hangrutschungen

Completed Research Projects

  • H. Hermerschmidt: Entwicklung eines Berechnungsmodells zur Untersuchung der Strömungsphänomene an Überfallschütz und drehendem Schaufelwasserrad, Dissertation, TU Braunschweig, 2019
  • S. Reinstädler: Modellierung und numerische Analyse der Entleerung von dünnwandigen Silos, Dissertation, TU Braunschweig, 2016
  • F. Pasenow: Modellierung oberflächengekoppelter Mehrfeldsysteme und numerische Analyse rutschender Bodenmaterialien, Dissertation, TU Braunschweig, 2014
  • A. Kölke: Modellierung und Diskretisierung bewegter Diskontinuitäten in randgekoppelten Mehrfeldsystemen, Dissertation, TU Braunschweig, 2005
  • C. Leppert: Mehrphasenmodell für granulare Medien zur numerischen Untersuchung des Phasenübergangs bei der Entleerung von Silos, Dissertation, TU Braunschweig, 2007