Effects of Rarefaction on the Shock Wave/Boundary Layer Interaction in Hypersonic Regime

摘要

Maneuverability of an aero-space-plane can be performed, besides by thrusters, also by aerodynamic surfaces on which a shock wave, generated on the front part of the vehicle, could impinge. This impingement produces on the surface local increases of heat flux and of aerodynamic load. The purpose of the present study is to evaluate the effects of rarefaction on the Shock Wave/Boundary Layer Interaction (SWBLI) in hypersonic regime. In rarefied regimes, in fact, the shock wave and the boundary layer are thicker than those in continuum, producing on the surface a more extended interaction zone. Furthermore, as the present analysis is carried out at Mach numbers typical of the reentry, a shock wave is much stronger than that usually met in supersonic, continuum flow. The study is carried on as a function of altitude in order to quantify the effects of both rarefaction and intensity of the shock wave on: extension of the interaction region, heat flux, aerodynamic load, slip velocity and slip temperature. The problem is studied computationally by the direct simulation Monte Carlo code DS2V. The flow field on a flat plate, on which a shock wave impinges, is simulated. The test conditions are those that should be met by the Flight Test Bed vehicle (FTB-X) along the re-entry path in the altitude interval 55-75 km. As expected, the extension of the interaction region increases with rarefaction. The maximum values of heat flux and aerodynamic load in the interaction region are about one order of magnitude higher than the same quantities without shock wave impingement and are comparable with those at the leading edge. The tests verified that the Neumann's analytical relation, linking the pressure rise to the heating rise in the interaction region, holds also in rarefied regime.