Fluid-structure interaction modeling: first applications at cnes

This paper deals with the numerical methodologies used at CNES DLA to set up Fluid-Structure Interaction (FSI) calculations. The numerical strategy developed is based on the code coupling which allows the communication between two specific codes. In fact, to model launcher's components, CNES uses various specialized codes (for thermal, mechanical, fluids, combustion applications, etc.), to seek individual solutions of the highly complex problem. Then, a third code allowing communication between computational fluid dynamics (CFD) and finite element analysis (FEA) (interpolations between different meshes) and exchanging shared variables (mainly, pressures and displacements) is required for FSI problems. One of the major application fields identified concerns the solid propulsion. Two problems are investigated to perform coupled calculations with increasing complexity. The first one is about the Solid Rocket Motor (SRM) ignition. This transient phase can be decomposed by successive steady-states with step-by-step increasing of internal motor pressure. This allows performing unidirectional coupling with both a script developed at CNES and the MpCCI software. The second one concerns thrust oscillations of SRM. A bidirectional approach is used to simulate the behavior of a flexible obstacle, made of elastomer, protruding in a cold gas flow of an experimental test bench developed to reproduce oscillating pressure phenomena at a reduced scale