Influence of Upstream Flow Perturbations on Blunt Fin Induced Shock-Wave / Boundary-Layer Interaction Unsteadiness

Detached eddy simulations were performed to study separation unsteadiness in a Mach 3, blunt fin induced shock-wave / boundary-layer interaction. Baseline simulations showed reasonable agreement with experimental measurements. The response of the separation unsteadiness to upstream flow perturbations was initially investigated by injecting synthetic turbulence, generated via a digital filter method, at the inflow boundary. A weak, but detectable correlation was found between the incoming turbulent fluctuations and the low-frequency separation motion. Inflow profiles of velocity perturbations, conditionally averaged based on separation motion, were used to design an artificial upstream time-periodic body force. With a forcing frequency representative of the characteristic large-scale separation unsteadiness in the baseline flow, the separation shock motion was phase locked to the applied force. These results demonstrate that upstream forcing of a certain form can modulate the separation motion of a strong interaction, where significant unsteadiness is exhibited even in the absence of upstream perturbations. These results are consistent with the findings from previous studies of weaker interactions, and imply possibilities for flow control of strong interactions.