Effects of strakes on a glancing shock wave/turbulent boundary-layer interaction

Abstract

Glancing interactions, between a turbulent boundary layer and shock waves generated by an unswept sharp fin with one of five different strakes, were examined at Mach 2.46. The aim was to investigate the effects of the strakes on the interaction behavior. The experiments involved surface pressure measurements, surface oilflow patterns and laser-light sheet pictures. An Euler computational fluid dynamics solver was used to help understand the in viscid-shock structures that play an important role in defining the interaction strength. The results show that a properly designated strake, which covers the whole of the root chord of the fin, has a weakening effect on separation. When a sharp fin is modified using a strake, the shock wave from the strake leading edge (strake shock) intersects the shock from the unmodified part of the model (fin shock) and bends it strongly towards the model. In order to prevent separation, a strake must be tall enough to prevent the finshock reaching the wall before the fin trailing-edge location. At the same time, the strake must be slender enough so that the strake shock itself does not cause separation. Based on these conditions, the strake dimensions needed to prevent separation have been predicted.