An unsteady shock-fitting technique based on unstructured moving grids

A shock-fitting technique based on unstructured moving grids is developed. Based on Arbitrary Lagrangian-Eulerian (ALE) equations, Discrete Geometric Conservation Law (DGCL) is constructed by adopting a new idea for modifying the volume; the field variables of new re-meshing grids are obtained by the information transfer method based on the unstructured moving grids technique; the initial shock position is determined by the flow field captured by the first-order spatial scheme and the unsteady flow is successfully simulated using shock-fitting technique. The fluid-structure coupled process of hypersonic fairing separation when Mach number reaches 6.0 is simulated using the shock-fitting and shock-capturing methods respectively, and the simulation results are good in agreement. With Mach number increased, the accuracy is hard to reach second-order unless by adjusting the limiter parameters or time step artificially. However, there is no abnormal occurring even if the Mach number reaches to 20.0 when the shock-fitting method is adopted. Comparing with the traditional shock-fitting technique, the unsteady shock-fitting technique can be used to simulate the irregular shock produced by complex shapes and the moving shock wave produced by the unsteady flow, it can also solve the stability problem which may generally occurred in the process of simulating the multi-body separation by the finite volume method (FVM ).