Flowfield structure characteristics of the hypersonic flow over a cavity: From the continuum to the transition flow regimes

Abstract

The cavity configurations produced by discontinuities at thermal protection system coated at surface of reentry space vehicles can lead to separation, attachment, and even transition of gas flows around the vehicle's surface, which can bring serious aerodynamic heating during the space vehicles reentering the Earth's atmosphere. In this paper, the continuum, slip, and transition flow regimes are chosen to represent reentry atmosphere environment and then a numerical investigation of hypersonic gas flows over a family of cavities is performed by using the direct simulation Monte Carlo method to reveal flow structures in the cavity flowfield under different length-to-depth ratios and freestream incoming Mach numbers. In particular, when the freestream varies from the continuum to the transition flow regimes, the minimal length-to-depth ratios required for cavity flow becoming the closed type are 8, 6, and 5, respectively. The effect of the freestream incoming Mach number on the cavity flow characteristics is getting weaker when the freestream varies from the continuum to the transition flow regime. The two significant findings are that the cavity flow characteristics under hypersonic conditions are primarily determined by cavity geometry rather than freestream incoming Mach number and secondly, effect of the freestream incoming Mach number on cavity flow type is very slight if the freestream is in the transition flow regime.