On stability and relaxation techniques for partitioned fluid-structure interaction simulations

Abstract

The stability of relaxation techniques has been studied for strongly coupled fluid-structure interaction (FSI) with application to a cantilever immersed in channel flow. The fluid is governed by Navier–Stokes equations for incompressible flow condition using turbulence modeling, and the solid is governed by the equation of motion with compressible material modeling. The applied kinematic description is Lagrangian for the solid and Eulerian for the fluid. The coupling of the state solvers is achieved by the Arbitrary Lagrange–Euler procedure, which involves a mesh motion solver, and the FSI procedure is stabilized by relaxation. It is shown that the stability can be related to the frequency shift caused by FSI, and they follow the same rate for the shape factor of the structure with an offset. The results correlate well to theoretical results and show that all relaxations fail for sufficient high-frequency shift for given mesh resolution. We also propose a continuation technique to stabilize the solution near the instability region, which improves efficiency and can be integrated easily for the black-box FSI solution procedure.