Laminar/Transitional Fin-induced Shock Wave Boundary-Layer Interactions at Mach 5

Abstract

An experimental investigation on Shockwave/Boundary Layer Interaction (SBLI) induced by an unswept fin is performed at Mach 5 with both laminar and transitional boundary layers. The unswept fin geometry is the scaled-down model (3:8) of the fin from the DLR STORT flight test program. A flat plate fin-induced SBLI is investigated at Rex = 2.50×10^6 (laminar) and Rex = 3.24×10^6 (transitional) in an indraft wind tunnel. Oil flow visualization, mean pressure, and unsteady pressure measurements are used to characterize the SBLI. Oil flow visualization and mean pressure measurements show strong similarities with turbulent interactions. The footprint of laminar/transitional SBLIs shows quasi-conical features and dependence on interaction strength. Mean pressure measurements show the two-dimensional free interaction theory also applies to the scaling of fin-induced SBLI examined here. Surface pressure fluctuations in the laminar SBLI show low frequency unsteadiness while the transitional case shows both low-frequency and Mack mode (second mode) fluctuations.