Fluid structure interaction with large structural displacements

The calculation of viscous flows inside deformable structures faces major difficulties when enforcing the kinematic compatibility at the fluid structure interface and updating the geometry of the domain. This paper proposes to overcome these problems by considering the fluid and the structure as a unique continuous medium, to be studied in a fixed reference configuration. The resulting problem is then split into a fluid and a structural part through an additive decomposition of the space of kinematically admissible test functions. This approach treats the structure in a fully Lagrangian way and uses an associated arbitrary Lagrangian Eulerian (ALE) formulation for the fluid. Such a strategy has three advantages which are detailed in the present paper. -bu it can be discretised in time by implicit, stable, energy conserving time integration schemes, and solved by simple, iterative uncoupled algorithms; -bu the fluid and the structural problems can be approximated by independent finite element spaces; -bu the most recent geometrically exact nonlinear shell models can be used for the structures. The full strategy has been implemented into an industrial CFD code. Results obtained in the simulation of industrial hydraulic shock absorbers are presented at the end of the paper.