An overlapping grid adaptive interface advancement method for hypersonic continuum-rarefied flow and its application

When the hypersonic aircraft flies in the transitional regime, both continuum and rarefied flows appear in the flow field around the aircraft. A multi-scale adaptive advanced overset grid method is proposed to deal with such a flow problem. The whole flow field is covered by the structured and unstructured grids which are independently generated in different scales. The adaptive hole cutting process is advanced by the cut-off value of the interface breakdown function of the continuum and rarefied flows in the structured grid. When the hole cutting process is completed, the rarefied regions are computed using the unstructured DSMC method while the continuum regions are computed using the structured CFD method based on the N-S equations. To couple the two algorithms, the flow information at the boundary between the continuum and rarefied regions is interpolated, exchanged and processed. According to the instantaneous solution of the coupled flow field, the overlapping parts of the different grids are advanced by the interface breakdown function. The feasibility and effectiveness of the present method are validated by the simulation results of the supersonic flow across a cylinder and hypersonic flow across a hollow cylinder-flare.