Tomographic Particle Image Velocimetry Measurements of Supersonic Boundary Layers over 3D Surface Curvature

The objective of this study is to quantify the effects of three-dimensional pressure gradients on supersonic turbulent boundary layers. The focus of the current paper is the application of particle image velocimetry (PIV) to several 3D rigid test articles representative of panel mode shapes that have undergone structural deformation due to aerothermal loads in the high speed regime. While recent work has quantified the modification of turbulent statistics due to 3D pressure gradients, the current work extends the investigation to consider the underlying structure of the boundary layer. Experiments have been performed at the Von Karman Facility Wind Tunnel D at Arnold Air Force Base. Comparisons are made to past stereoscopic particle image velocimetry (SPIV) experiments and companion Computation Fluid Dynamics (CFD) simulations of the 3D curvature test articles, examining both surface pressure and off-body mean velocity response to the surface curvature. Two-point correlations of fluctuating velocity from the tomographic particle image velocimetry (TPIV) data indicate minimal influence of the surface curvature on the spanwise extent of correlated motions. Isocontours of the instantaneous 3D velocity fields from TPIV are inspected for evidence of streamwise evolution through the concave curvature.