Flow visualization in a streamline-traced supersonic inlet

Internal flow structures of a streamline-traced inlet were investigated by measuring wall pressure and visualizing flow structures using planar laser Rayleigh scattering technique (PLRS) in Mach 3.3 flows. Numerical solutions of the flowfield proposed by Busemann were used to design the inlet model. The experiment was conducted at two different Reynolds numbers for the freestream. PLRS images revealed flow features such as a termination shock wave, counter-rotating vortex pairs (CVPs), separation bubbles, and the turbulent boundary layers inside the inlet model. The wall pressure measurement showed a good agreement with the numerical solution of the Busemann flowfield. Pseudo cross-sectional images were constructed by using thin slices of the PLRS images to further investigate the flow structures. In the vertical pseudo cross-sectional images, flow structures of the CVPs were found similar to ones presented in a previous study. In the horizontal pseudo cross-sectional images, it was found that the size of the separation bubble changed at different Reynolds numbers of the freestream. The authors believe that the PLRS images presented herein are the first "side-view" images of the flowfield of a Busemann type inlet.