MEASUREMENTS OF COMPRESSIBLE TURBULENT-FLOW STRUCTURE IN A SUPERSONIC MIXING LAYER

Multiple overheat cross-wire, parallel hot-wire, shadowgraph image processing and high-frequency response pitot probe surveys were taken in a two-dimensional, adiabatic, supersonic, free mixing layer, consisting of Mach 1.8 air (Re = 7 x 10(6)/m) injected tangentially into a Mach 4.0 freestream (Re = 67 x 10(6)/m). Mass flux turbulence intensity profiles in three dimensions were acquired, and the axial component was found to be about 25% larger than the transverse and spanwise components. Mean Favre-averaged velocity fluctuation data indicated that the axial component was negative, while both the transverse and span were positive. Turbulent flow structure angles and length scales were measured in the fully developed region of the how The structure angles were found to be consistent with previous compressible boundary layer results; however, the magnitude here was found to decrease across the mixing layer Mach number fluctuation levels were also measured. The peak Mach number fluctuation level in this bow was about 10%.