The effect of walls on instability waves in supersonic shear layers

A spatial stability analysis is performed to determine the effect of wall placement on instability waves in confined supersonic shear layers. It is shown that the growth rates of Kelvin-Helmholtz instability waves are independent of wall height. However, supersonic instability waves are found to exhibit peaks and valleys in their growth rate curve as a result of the reinforcement and cancellation of the reflected Mach waves at the shear layer. Finally, it is shown how the instability growth rates in a ducted shear layer may be maximized by the proper choice of the duct width to height ratio.