An extended stratified flow model with multiple Riemann solvers for compressible Fluid-Elastic Interactions

In flow-structure interactions (FSI) with strong impact or strong shock wave, compressibility effects often need to be considered. In our earlier works, based on a cut-cell based sharp-interface method (Chang, Deng & Theofanous, JCP 2013), various Riemann solvers have been applied for linearly elastic (Tao & Deng, IJCM 2017) and elastic-perfectly plastic materials. In the current work, to improve the efficiency, flexibility and applicability in solving complex FSI problems, a robust method based on the stratified multiphase flow model (Chang & Liou, JCP 2007) is developed to simulate compressible fluid-elastic interactions in pure Cartesian grid. In this method, a volume fraction is used to differentiate each phase, and the reconstruction of volume fraction is performed on each cell face for flux calculations. A set of equations subjected to this model are solved with the finite volume method and a series of Riemann solvers. The AUSM+-up scheme, the exact linearly elastic Riemann solver, and an exact two-phase Riemann solver are used to calculate the numerical fluxes in fluid, elastic solid, and at the fluid-solid interface, respectively. Validations with several 1D, 2D and 3D problems show the accuracy and robustness of this method.