The effect of walls on a spatially growing supersonic shear layer

Abstract

The inviscid instability, with respect to supersonic disturbances of a spatially growing plane mixing layer inside parallel flow guide walls, is investigated using linear stability analysis. For supersonic convective Mach numbers, it is found that the maximum amplification rates of the shear layers approach an asymptotic value and that this maximum amplification rate increases to its maximum value and decreases again as the distance between the walls decreases continuously. Contour plots of the pressure perturbation fields indicate that there are waves propagating outward from the shear layer along the Mach angle, and that the walls provide a feedback mechanism between the growing shear layer and this compression/expansion wave system. The streak lines of the flow confirm that the spreading rate of the shear layer is unusually small for supersonic disturbances.