The influence of shock layer instability on surface heat transfer in hypervelocity flows and its relevance in planetary entry vehicle design

Curved bow shocks generate shear layers with smoothly distributed vorticity via the baroclinic mechanism. The magnitude of the vorticity in the shear layer is proportional to the density ratio across the shock, which may be very large in hypersonic flows. The instability of such a shear layer may lead to large-scale alteration in the flowfield. Previous research has identified the nonlinear growth mechanisms in such flows, and has qualitatively assessed the impact on inviscid flow structure. However, to date the influence of such instabilities on laminar, convective heat transfer has not been addressed. The focus of this paper is to examine the influence of this large-scale shear layer instability on laminar convective heat transfer for blunt bodies in hypersonic flows with high density ratios. Understanding the impact of this instability on surface heat transfer is crucial for entry into planetary atmospheres whose thermochemistry admit high density ratios, of which carbon dioxide is but one example. Fundamental observations drawn from the model problem of hypersonic flow over a 30° wedge are considered in the context of hypersonic planetary entry into various atmospheres.