FS-Interaction

The coupling of flow and structural analysis is indispensable in many areas, but less important or necessary in others. Since two different numerical methods are generally used to solve the two problems, the finite volume and finite element methods, an integrated approach is less suitable and therefore unusual. With rigid structures, feedback to the flow field can be neglected; an unilateral multidisciplinary simulation is sufficient.

In other cases, however, there is a reaction which requires bilateral treatment. Until corresponding regulation changes were introduced, it was common in Formula 1, for example, to design the front and rear wings in such a way that the profiles would deform favourably in terms of flow resistance with increasing pressure load, so that a higher final speed could be achieved. At the same time, sufficient downforce for high corner speeds was maintained in slow passages.

Since the two simulations describe different areas (domains), fluid volume on the one hand and structural components on the other, separate meshes are necessary in each case. For data exchange, the decisive factor is whether these meshes are compatible at the common contact surfaces, which means equal nodes and element surfaces, or incompatible. In the second case, the results must also be interpolated between the different meshes during transmission. Due to the significantly greater flexibility in modeling, working with incompatible meshes is the preferred option. The additional numerical effort for interpolation is accepted.

In a unilateral multiphysics simulation, the local pressure conditions from the flow analysis are passed on to the structural analysis. In a bilateral link, the deformation of the structure is returned to the flow simulation to update the topology of the fluid volume.