Non-Rankine-Hugoniot Shock Zone of Mach Reflection in Hypersonic Rarefied Flows

This study investigates the non-Rankine-Hugoniot shock zone of Mach reflections in hypersonic flows with different flight altitudes using the direct simulation Monte Carlo method and Navier-Stokes approach. In the non-Rankine-Hugoniot shock zone, the flow viscosity induces the numerical deviation from the inviscid theoretical value with a smooth and continuous variation. It is determined and illuminated by comparing it with shock polars. A suitable and novel definition of the height of the non-Rankine-Hugoniot shock zone is then derived to facilitate the study of its size. The computations demonstrate that the height of the non-Rankine-Hugoniot shock zone grows as flight height increases, whereas a reduced Mach stem is observed. The growth of the non-Rankine-Hugoniot shock zone can be explained by the increase in the curvature of shock waves in the three-shock intersection. Computational results show the existence of a strong pressure hot spot and a weak temperature hot spot near the triple point and reveal that the slipstream starting from the triple point divides off these two hot spots. The peak values in the hot spot only fluctuate within a small range with increasing flight altitude. The direct simulation Monte Carlo results of additional cases indicate that rarefaction caused by the reduction of computational size does not affect the peak value in the hot spot.