Stereoscopic PIV measurements of a turbulent compressible mixing layer for CFD validation

In the present study, a two-stream compressible mixing layer with convective Mach number (M_c) of 0.53 is investigated with stereoscopic particle image velocimetry (SPIV) and additional flow diagnostic techniques. The experiment is performed in a blowdown supersonic wind tunnel facility with a primary stream Mach number of 1.57 and secondary stream Mach number of 0.33. The two streams and their boundary layers, initially separated by a splitter plate, begin mixing at the splitter tip. SPIV measurements are taken on the spanwise central plane from the onset of mixing to past shear layer fully-developed conditions. Instantaneous images are processed to produce mean three-component velocity vector fields and ensemble-averaged turbulence statistics. Flow visualization results show that, at this convective Mach number, there are no clear two-dimensional roller structures that are present at lower convective Mach numbers. Instead, the turbulent structures appear more random and three-dimensional. Mean streamwise velocity and Reynolds stress profiles exhibit self similarity in the fully developed region. Velocity measurements show that the normalized growth rate value falls in line with the trend of previous experimental data versus Mc. In addition, streamwise, transverse, and spanwise normal Reynolds stresses (Re_xxRe_yyRe_zz) as well as the primary shear stress (Re_xy) peak values are all close to previously documented values near M_c = 0.53. Rexx has the highest stress magnitude, followed by Re_zzRe_yyand Re_xy.