Numerical Investigation of Hypersonic Wall-Bounded Shear Flows - Part 2: Entropy-Layer Instability in Blunt Cone Flows

Abstract

The entropy-layer instability of an axisymmetric blunt cone flow at Mach 8 is studied numerically for the free-stream conditions of the experiments of Stetson et al. Weakly amplified disturbances dominated by temperature and density fluctuations inside the un-swallowed entropy-layer are found at the same frequencies as in experiment. The corresponding amplitude functions have a distinct maximum at a generalised inflection point located in the entropy layer above the viscous boundary layer as noted by Stetson et al. The numerical results show that this entropy-layer instability mode is most amplified for zero wave angle. Downstream of the position where the entropy layer has been swallowed by the growing boundary layer these entropy-layer instabilities are damped.