Structure and Dynamics of Bleed-Controlled Impinging Shock/Turbulent-Boundary-Layer Interactions

Porous boundary-layer bleed alleviates the detrimental effects of shock/turbulent-boundary-layer interactions (SBLIs) in high-speed vehicles. However, many underlying mechanisms through which bleed influences SBLI dynamics remain poorly understood, including unsteady separation mitigation, effects on low-frequency spectra, and turbulent kinetic energy (TKE) modulation. Proper resolution of the dynamics of these phenomena motivates the use of wall-resolved large-eddy simulations. The configuration is based on experiments at Mach 2.5 and a momentum-thickness Reynolds number of 2800, on which a shock of flow-deflection angle of 8 deg impinges. Porous bleed patches are considered with resolution of the flow structure in individual holes. Two different suction strengths are examined, denoted “half-” and “full-bleed” cases based on the sonic mass flow coefficient. Although both bleed cases localize and reduce the mean reversed flow region, only the full-bleed case successfully reduces unsteadiness, TKE, wall-pressure loading, and overall distortion due to the SBLIs. These distinctions are reflected in various local and global effects of bleed, which are examined with three-dimensional modal analysis. Among the key findings is energy shifting from the low-frequency separation behavior to a higher-frequency signature, which modulates the bleed-associated shocks and expansions. Overall, the study highlights the complex interactions between individual bleed-hole flow structures that cumulatively yield the observed overall effects, which are important in optimizing bleed systems for various design objectives.