Exploring the Structure and Dynamics of Shock/Turbulent Boundary Layer Interactions Generated by Swept Compression Ramps in a Mach 2 Freestream

This thesis reports the investigation of the unsteadiness of a 2D and 3D swept shock-wave/turbulent boundary layer interaction (STBLI) and the effect the extent of subsonic flow has on the separation location. Two swept compression ramp cases are investigated at Mach 2 freestream conditions – a high sweep of 30 degrees and a low sweep of 10 degrees both having the same compression angle of 22.5 degrees in the vertical plane. Using a number of diagnostic techniques including stereoscopic and planar particle image velocimetry (PIV) and unsteady pressure sensitive paint (PSP) anchored with pressure transducers, the unsteadiness, the extent of subsonic velocities, and the streamwise point of separation are all measured inside the separation bubble. The differences between the quasi-conical and quasi-cylindrical separation regions resulting from the different sweep cases are further investigated. The subsonic extent and the separation point were found to have a linear correlation with one another, and the correlation decreases with increasing sweep angles from an average of 0.47 at the lower sweep to 0.33 at the higher sweep. Furthermore, the unsteadiness was found to shift to higher frequencies as the sweep angle increased, with dominant frequencies of approximately 0.7 kHz at the lower sweep and a range of 0.7 to 2.2 kHz at the higher sweep. When increasing the sweep angle, the crossflow velocities approximately tripled from a value of 50 m/s in the lower swept case to a value of 140 m/s in the higher swept case at the boundary layer height of y = 2 mm, and at y = 8 mm the crossflow velocities approximately doubled from 50 m/s to 100 m/s.