Visualization of scoop inlet-induced circular isolator flows using planar laser Rayleigh scattering imaging

The visualization of scoop model inlet-induced circular isolator flows was performed using a planar laser Rayleigh scattering (PLRS) imaging technique at a hypersonic flow facility. The scoop model was designed for a cruise Mach number (Ma) of 6. Two contraction ratios of the scoop inlet, 4 and 5, were investigated at various unit length Reynolds number (Re_ℓ) conditions. Two freestream Ma = 4.5 and 6 were tested to investigate the robustness of the scoop model inlet for the off-design conditions. Pseudo-three-dimensional flow structures of the isolator were constructed by using averaged planar images from multiple two dimensional imaging planes. The visualization showed that Re determines the thickness of the boundary layer and the size of eddies. Similar overall flow and shockwave structures were observed for different Ma and Re conditions, which are indicative of the robustness of the scoop inlet. Curved shockwaves and localized flow separation were inferred from the flow visualization. Differences in shockwave angles, shock impinging location, the size of the core flow, and the size of the flow structure were discussed. The experimental results were compared with the results from large-eddy simulations, which confirmed the inferred flow structures.