The current computational resources lead the different scientific disciplines to get closer to each other, in order to consider more and more complex phenomena. Thus, one of the axis of research of the CFD Team from École Centrale Nantes is the Fluid-Structure Interaction (FSI). In this context, the development of a large displacement structural solver for elongated bodies and its coupling with the non-structured finite volume RANSE solver, ISIS, has been done. This thin beam solver relies on the Cosserat theory and on the 'geometrically exact' approach. The space coupling on the interpolations and the information transfer at the fluid-structure interface were realised with caution, in order to be as accurate as possible and to fulfill the load conservation. Since the beam solver can be used for great displacements, an original technique had to be built to update the fluid computational domain. It is based on the pseudo solid approach, which allows a precise control over the mesh deformation through a local behaviour law of the pseudo-solid. Each part of the FSI code has been checked: the structural solver on 2D/3D test-cases, in statics and in dynamics, in small and large displacements; the remeshing module has been tested on various geometries and with MPI. Finally, some FSI applications have been performed: two bidimensional examples, a steady case and a fully unsteady one; then, the program has shown its capabilities in 3D on a deformable cable in a current with a fixed end. The computation of a riser towed in a multifluid environment at rest has also been done and studied.
