Experimental Characterization of Asymmetric Flow in Rectangular Cavities at Supersonic Speeds

Yawed inflow is common in practical applications, yet its influence on coupled flow–acoustic dynamics in supersonic open cavities is not fully understood. The present study examines how yaw angle variation influences the unsteady behavior of a shallow open rectangular cavity at Mach 2. Time-resolved surface-pressure measurements and oil-flow visualization were acquired over a yaw range of Ψ = −10◦ to +10◦ to characterize both low and high-frequency flow features. At the symmetric condition (Ψ = 0◦), the cavity exhibits a slow, stochastic bistable mode in which the floor vortex alternates between clockwise and counter-clockwise orientations, producing enhanced low-frequency energy. Consistent signatures at spanwise-separated aft wall sensors indicate that this switching is accompanied by lateral redistribution of low-frequency pressure activity. A yaw misalignment as small as ±1◦ suppresses this bistability and stabilizes the vortex orientation. At higher frequencies, narrowband spectra reveal well-defined Rossiter modes whose amplitudes depend strongly on yaw, while Short-Time Fourier Transform analysis shows intermittent, spanwise-asymmetric energy bursts at zero yaw that disappear once yaw is introduced. These insights enhance the physical understanding needed for modeling and managing cavity-induced unsteadiness in high-speed aerodynamic applications.