Modal analysis of a shear layer in high-supersonic cavity flows using data-driven and operator-based resolvent analysis

Shear layer oscillations (SLO) are common phenomena in aerospace applications inducing unfavorable acoustic radiation and structural fatigue. SLO driving mechanism over open cavity flows at subsonic and supersonic speeds has been well studied. However, for SLO over a cavity in high supersonic flows, the stability properties are relatively unexplored, i.e., for flow regimes beyond Mach 3. The classical Rossiter model fails to predict the SLO characteristics. Therefore, in this work resolvent analysis has been employed to identify the dominant dynamic mechanisms and modal characteristics of self-sustained SLO at high Mach numbers. In particular, the resolvent analyses are performed using data-driven and operator-based frameworks. The comparisons between both implementations will be highlighted for the resolvent modes and spectra. We will also discuss the influence of the baseflows due to the differences in the solver fidelity. With a series of implicit large-eddy simulations at Mach numbers 2 to 5, we observe a weak coupling between standing waves within the cavity and SLO. The strong compression/expansion waves on the shear layer and cavity wall reflected Mach waves significantly contribute to the SLO characteristics.