Effect of Shock Strength on the Unsteadiness of Mach 5 Shock/Boundary-Layer Interaction Using Fast-Response PSP and High-Speed PIV*

Shock/boundary-layer interaction (SBLI) is known to exhibit large-scale, low-frequency unsteadiness. There have been a number of candidates identified as the driving mechanism of the low-frequency shock unsteadiness. Some researchers have argued that whether upstream or downstream mechanisms dominate depends on the strength of the interaction. The current study is an experimental investigation that aims to investigate the upstream and downstream flow effects on the SBLI unsteadiness and to identify how the importance of different mechanisms differ at two different shock strengths. In this study, SBLI was induced by compression ramps of 28 and 26.5 degree in Mach 5 flow. For these flows, the mean separated flow length scales are 3.3 and 1., respectively. The surface pressure was obtained using 20 kHz fast-response pressure-sensitive paint (PSP) and the velocity field was measured using planar and tomographic particle image velocimetry (PIV). Various correlation analyses between the shock foot motion extracted from PSP and the pressure fluctuations will be shown. In addition, low-order reconstruction of the velocity field using proper orthogonal decomposition (POD) will be used to explore differences in the characteristic large-scale flow structures.