THE INFLUENCE OF WALL COOLING ON HYPERSONIC BOUNDARY-LAYER SEPARATIONAND STABILITY

The effect of wall cooling on hypersonic boundary-layer separation nea r a compression ramp is considered. Two cases are identified correspon ding to the value of the average Mach number (M) over bar across the u pstream boundary layer approaching the compression ramp. The flow is r eferred to as supercritical for (M) over bar > 1 and subcritical for ( M) over bar < 1. The interaction is described by triple-deck theory, a nd numerical results are given for both cases for various ramp angles and levels of wail cooling. The effect of wall cooling on the absolute instability described recently by Cassel, Ruban & Walker (1995) for a n uncooled wall is of particular interest; a stabilizing effect is obs erved for supercritical boundary layers, but a strong destabilizing in fluence occurs in the subcritical case. Wall cooling also influences t he location and size of the separated region. For supercritical flow, progressive wall cooling reduces the size of the recirculating-flow re gion, the separation point moves downstream, and upstream influence is diminished. In contrast for the subcritical case downstream influence is reduced with increased cooling. In either situation, a sufficient level of wall cooling eliminates separation altogether for the ramp an gles considered. The present numerical results closely confirm the str ong wall cooling theory of Kerimbekov, Ruban & Walker (1994).