Entropy-layer instabilities over a blunted flat plate in supersonic flow

Entropy-layer instabilities in the supersonic flow over a blunted flat plate with a nose radius of $R_n\text{=2.5\hspace{0.17em}}\mathrm{mm}$ at a Mach number $\text{M=2.5}$ and a unit Reynolds number $\mathrm{Re}{\text{/l=9.9×10}}^6/\mathrm{m}$ are investigated. A type of entropy-layer instability most amplified at zero wave angle is found. Its streamwise wave number and the wall-normal phase distribution of the numerically obtained density eigenfunctions agree with flow-field visualization using the Schlieren technique. The frequencies of this entropy-layer instability made nondimensional on the basis of an appropriate entropy-layer length scale matches documented experimental observations at a blunted cone.