Oblique Shock Wave/Turbulent Boundary Layer Interaction: Information-Theoretic Approach

One of the most critical phenomena that affects supersonic flight and engine performance is shock wave/turbulent boundary layer interaction (STBLI). STBLI is a highly unsteady phenomenon constituted by a complex interaction between the shock wave, the boundary layer, and the turbulence structures. In this work, we study the interaction of an impinging oblique shock wave on a supersonic zero-pressure gradient turbulent boundary layer, and the resulting low-frequency unsteadiness of the shock wave and the separated region of the flow. The STBLI is simulated using explicit-filtering large eddy simulations (EFLES). To avoid any spurious upstream influence, we simulate the transition of a laminar boundary layer to a turbulent boundary layer using a constant body-force based tripping method. Using the simulated LES data and applying the information-theoretic measure of transfer entropy, we examine the directional causal influence on the dynamics of separation shock and bubble size in the STBLI. Our analysis reveals a directional information-theoretic coupling in which expansion-fan-induced velocity fluctuations modulate large-scale shock motion, while shock-driven disturbances exert a predictive influence on the unsteady breathing of the separation bubble in the STBLI.