On the low-frequency unsteadiness in shock wave–turbulent boundary layer interactions

The shock wave–turbulent boundary layer interaction over a compression corner is studied using global stability analysis (GSA) and resolvent based on separation of scales between the low-frequency, large-scale motions turbulent fluctuations. GSA identifies leading stationary mode, which becomes globally unstable as ramp angle beyond critical value. For stable flows, captures two-dimensional three-dimensional local maxima in optimal gain, both are due to modal resonance forcing mode. Notably, frequency-premultiplied gain associated with disturbances peaks at low frequency. different strengths, peak frequencies collapse onto universal value 0.015 when non-dimensionalized length region free-stream velocity. A numerical simulation perturbed corresponding reveals that response form back-and-forth motion.