Velocity field characteristics in supersonic mixing layers

Abstract Several compressible mixing layers, with one supersonic and one subsonic streams, are experimentally analyzed by pressure measurements and laser anemometry. Detailed measurements of the mean and fluctuating velocity fields are provided and compared against data from incompressible flows. The effects of compressibility on the flows are observed. The spreading rate of the mixing layers decrease when the Mach number is increased, in good agreement with results found in the literature. Laser Doppler measurements are performed for three test cases. The compressibility effects on the fluctuation levels are discussed and compared with existing results. The evolution of the turbulence structure of the flow, when the convective Mach number increases, is considered in the analysis when separate LDA seeding regimens are employed on the two sides of the layers. Some modifications of the large scale organization are observed when supersonic and subsonic mixing layers are compared and the two sides of the supersonic mixing layers have different characteristics.