COMPRESSIBLE TURBULENCE MEASUREMENTS IN A HIGH-SPEED HIGH-REYNOLDS-NUMBER MIXING LAYER

To assess the significant physics associated with compressible turbulence, extensive multiple overheat cross/normal-wire, shadowgraph image processing and conventional probe surveys were obtained in a two-dimensional, supersonic, free mixing layer, which consisted of Mach 1.8 air (Re/m = 7 x 10(6)) injected tangentially into a Mach 4.0 freestream (Re/m = 67 x 10(6)). A turbulence transformation was developed that allowed direct measurement of the total Reynolds shear stress. Profiles of three-dimensional turbulent shear, apparent mass, and heat flux data were acquired. Compressibility was found to account for 75% of the total compressible Reynolds shear stress (i.e., the incompressible term, rho u'v'BAR, accounted for only 25%) and 100% of the turbulent heat flux in the present nominally adiabatic flow. These data allowed the development and experimental evaluation of various turbulence closure formulations. The incompressible models yielded results consistent with measured incompressible terms. The Situ-Schetz compressible model accurately represented the total shear. However, the present data indicated that this model provided poor estimates of the turbulent heat flux. Hence, the Situ-Schetz techniques were generalized to consistently account for compressibility in all of the conservation equations. The performance of the new model was found to be excellent. New compressible turbulent kinetic energy formulations were also developed and evaluated.