Similarity in supersonic mixing layers

This paper deals with similarity and parameterization in supersonic shear layers with isothermal freestreams, when the Mach number M (based on the velocity difference Al/ across the layer) is M > 3. With the support of modeling results and experiments, it is argued that under these conditions the turbulent velocity fluctuations are controlled by the local sonic speed, and the rms fluctuating Mach number Mt approaches a saturation limit. These conditions permit inference of similarity laws and parametric expressions for the shear layer growth, maximum centerline magnitudes of temperature (or density), and Reynolds stresses. Turbulence closure simulations are shown to corroborate the proposed similarity theory and parameterization. An extension of the theory for mixing layers with different densities in the freestreams is also proposed.