Low-Frequency, Spanwise Oscillation in a Finite-Width Cavity*

A joint experimental–computational program examined low-frequency, spanwise oscillations in supersonic flow over a finite-width cavity. Lowpass-filtered rear wall surface pressure revealed that shear layer impingement was most often biased to one side of the wall, switching sides at a frequency two orders of magnitude below resonance. Therefore, a bifurcation into two spanwise-asymmetric, mirrored, quasi-steady states could be defined. The states were described by biased impingement/ejection near the rear wall, asymmetry of the shear layer, and centrifugal inner-cavity flow. Resonance amplitudes were also found to be spatially modulated by the low-frequency flow switching. A yawed inflow was found to force one of the asymmetric states.