Boundary Layer Separation on a Hollow-Cylinder/Flare at Mach 5

A θ = 15◦ hollow-cylinder/flare model is assessed in Mach 5 flow at a range of Reynolds numbers, 1.2 × 106 < ReL < 3.7 × 106. The laminar upstream boundary layer is subjected to SBLI-induced separation and develops transitional effects near reattachment on the flare surface. The influence of the flow is assessed using measurements of the surface temperature evolution via IR thermography and fast-response surface pressure measurements. A significant peak in heat transfer is observed near reattachment which moves upstream as Reynolds number increases. In addition, streamwise streaks are identified near reattachment that also move and scale-azimuthally with Reynolds number. Two modes in unsteady pressure on the flare surface are identified, centered at StL 3 and 15, investigation of their specific source is ongoing. Finally, streaks are visualized using the dominant first POD mode, and indicate that the coherent streamwise streaks pass along much of the flared surface, beyond just at the streamwise mean heat transfer peak location.