Mach Independence of Entropy Layer Instabilities
摘要
The entropy layer in a hypersonic flow over a blunted body is investigated using a high-accuracy spectral shock-fitting algorithm that solves the Euler equations within the shock layer. The base flow is computed via a direct numerical solution of the nonlinear equations. The analysis pays particular attention to the physical phenomena that arise at geometric discontinuities in body curvature. The flow field around a blunted 30-degree half-angle wedge, used as a representative body, is examined in detail and compared to viscous direct numerical solutions to evaluate the effect of viscosity on the profile of the entropy layer. Instabilities associated with the generalized inflection point in the entropy layer are investigated using linear stability theory. The entropy layer instabilities are shown to exhibit Mach number independence under a proper normalization. Our findings may be particularly useful for relating experimental results at different Mach numbers where the cold flow (calorically perfect gas) assumption is applicable.