Measurements of a Mach 3.4 turbulent boundary layer using stereoscopic particle image velocimetry

Experiments were performed within the Rutgers University Mach 3.4 supersonic wind tunnel to quantify the turbulent boundary layer in the test section, using stereoscopic particle image velocimetry (SPIV). Seeding of the tunnel was accomplished using atomized mineral oil, resulting in a Stokes number of 0.09. The Reynolds number based on momentum thickness and the friction-velocity Reynolds number were 64,000 and 4320, respectively, marking this as a high Reynolds number boundary layer. SPIV measurements were capable of resolving the mean velocity profile, along with turbulence quantities, permitting comparison against the known literature. Furthermore, the convection of vorticity concentrations representing hairpin vortices was observed within instantaneous vector fields. The resulting Reynolds stresses demonstrate that the boundary layer had typical values of anisotropy, while comparing well with data obtained within a slightly adverse pressure gradient. This was particularly noticeable from the trends in the Reynolds stresses, which exhibited higher-than-expected peak levels. These data provide a unique measurement of a supersonic turbulent boundary layer at Reynolds numbers not often encountered within existing data sets. [GRAPHICS] .