Kw. Cassel et al., THE INFLUENCE OF WALL COOLING ON HYPERSONIC BOUNDARY-LAYER SEPARATIONAND STABILITY, Journal of Fluid Mechanics, 321, 1996, pp. 189-216
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).