Centrifugal-Rossiter Interactions in an Open Cavity Flow

This study investigates the nonlinear dynamics of an open cavity flow, specifically addressing the origin of side peaks observed around the Rossiter modes. A spanwise-periodic direct numerical simulation (DNS) at Mach 0.5 and a length-to-depth ratio of two is utilized to examine the interactions between centrifugal instabilities and Rossiter modes. By employing spanwise-decomposed multitaper spectral proper orthogonal decomposition (SPOD), we isolate multiple low-frequency, three-dimensional centrifugal modes and associate each peak observed in the spectrum with its spanwise wavenumber. The triadic resonance condition is precisely satisfied between the side peaks, centrifugal modes, and the Rossiter modes within each spanwise wavenumber. We utilize triadic orthogonal decomposition (TOD) to analyze the energy transfer of inter-wavenumber triad interactions. The modal energy budget confirms that the centrifugal instabilities energize the Rossiter modes, forming inter-wavenumber frequency triads.