VELOCITY-FIELD CHARACTERISTICS IN SUPERSONIC MIXING LAYERS

Several compressible mixing layers, with one supersonic and one subson ic streams, are experimentally analyzed by pressure measurements and l aser anemometry. Detailed measurements of the mean and fluctuating vel ocity fields are provided and compared against data from incompressibl e 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. Las er Doppler measurements are performed for three test cases. The compre ssibility effects on the fluctuation levels are discussed and compared with existing results. The evolution of the turbulence structure of t he flow, when the convective Mach number increases, is considered in t he analysis when separate LDA seeding regimens are employed on the two sides of the layers. Some modifications of the large scale organizati on are observed when supersonic and subsonic mixing layers are compare d and the two sides of the supersonic mixing layers have different cha racteristics.