Characterization of shock wave turbulent boundary layer interaction using particle image velocimetry

A method for the use of Particle Image Velocimetry in the Rutgers Supersonic Wind Tunnel is established and described. The use of ice crystals as PIV seed material is tested using an oblique shock as a step response to estimate the particle lag time and particle diameter. These values were found to be 2.8 µs and 0.43 µm respectively. The Stokes number was found to be St = 0.11. The statistical properties of the undisturbed boundary layer are determined using PIV data and simplifying assumptions. The boundary layer thickness is δ = 15.6mm and the free stream velocity is U1 = 621m/s. This velocity corresponds to an approximate Mach number of 3.22. Using the Clauser method, the shear velocity is u = 22.45m/s. The log-law region has a last reliable point at height y+ ≈ 500 and extends to y+ ≈ 3000. Velocity fluctuation values and trends are in agreement with published results. Investigation of streamwise XY planes of the boundary layer suggest the existence of coherent structures, particularly hairpin vortices. Galilean decomposition clearly shows vortex structures at height y/δ≈0.2 at a convection velocity of Uc/U∞ = 0.75. Investigating a spanwise XZ plane at height y/δ=0.1 shows coherent regions of high and low velocity which stretch beyond the field of view. Shock Wave Turbulent Boundary Layer Interaction is investigated in the case of a 6 and 9 degree angle of attack flat plate used to generate an oblique shock which impinges upon the turbulent boundary layer. In the 9 degree case, an average separated region of the boundary layer exists to be 2.11δ long in the streamwise direction and exhibits the characteristics of a strong interaction. Ahead of the separated region, a separation shock shows streamwise motion of about ±0.25δ. The 6 degree case shows no boundary layer separation in the mean flow. A reflected shock exhibits reasonably steady behavior which is characteristic of a weak interaction. The sonic line shows that the subsonic layer dilates to a height of y/δ=0.27 and y/δ=0.7 for the 6 and 9 degree case respectively. In both interactions, the recovery of the boundary layer extends beyond the field of view in the streamwise direction.M.S.Includes bibliographical referencesby Douglas E. Ojal