Unsteady Flow Features Across Different Shock/Boundary-Layer Interaction Configurations

An experimental study has been conducted to investigate unsteady flow phenomena observed within various two-dimensional configurations of shock/boundary layer interactions. Six configurations have been tested in Mach 2 flow: ϕ1 = 14◦ and 20◦ compression ramps, and incident shock reflections from ϕ1 = 7◦ , 8 ◦ , 9 ◦ , and 10◦ shock generators; Reynolds numbers in each case are Reθ ≈ 8350. The flow is assessed using an array of fast-response pressure transducers in conjunction with a high-repetition rate PIV system. Development of the mean flow structures early in each interaction is observed to be consistent with the Free Interaction concept. Unsteady wall-pressure energy content at frequencies above those associated with the characteristic low-frequency shock motion also show significant similarities in the vicinity of the shock foot. Results confirm that this low-frequency peak is not associated with a narrow-band forcing mechanism from either upstream or downstream, but rather a characteristic frequency that varies with interaction strength, which describes the flow’s dynamic response. These findings support various models published in literature that have sought to explain the source of low-frequency unsteady shock motion.