Empirical Correlation for Hypersonic Aerodynamic Heating in Open Cavity Geometries Under Rarefied Flow Conditions

Abstract

Aerodynamic heating measurements were taken during hypersonic shock tunnel and suborbital tests within two open cylindrical cavity geometries with effective L/D ratios less than 1.2. Examined variables included angle of attack, free stream density and Mach number. The test data indicate a free stream Reynolds number based relationship between the heating inside the cavity and stagnation heating. This relationship was observed for both cavity configurations and was more pronounced for lower angles of attack. The relationship was not observed for Knudsen numbers greater than 0.1, which represents the onset of slip flow conditions. Since the correlation allows for prediction of cavity heating to within 25%, it indicates the possibility of using an empirical correlation to estimate cavity heating under rarefied aerodynamic heating conditions. This could reduce the need for costly Computational Fluid Dynamics analyses to simulate cavity heating under near slip flow conditions.