Determination of entropy-swallowing point of blunt hypersonic cone

Abstract

Entropy swallowing is the phenomenon where the entropy layer is swallowed by the boundary layer developing downstream. In this work, the entropy-swallowing point over a 5° blunt hypersonic cone is investigated theoretically and numerically. An equation for obtaining the location of the entropy-swallowing point is derived herein that requires only the free-stream parameters. This equation also reveals the relationship between the entropy-swallowing point and the nose radius under the constant free-stream Mach number. The analytical results are entirely consistent with direct numerical simulation results. Furthermore, the influence of the Mach number and Reynolds number on the entropy-swallowing point is investigated. The location of the entropy-swallowing point depends more strongly on the Reynolds number than on the Mach number, with the entropy-swallowing point shifting further downstream as the Reynolds number increases. However, as the Mach number increases, its impact on the entropy-swallowing point decreases. Furthermore, the influence of the boundary-layer displacement also decreases with an increase of the Mach number.