Spectral Proper Orthogonal Decomposition of Transitional Flow Over an Open Cavity

This study investigates boundary layer transition over an open cavity under subsonic flow conditions, motivated by the economic and environmental impact of reducing aerodynamic drag. Using Direct Numerical Simulation (DNS), Linear Stability Theory (LST), and Spectral Proper Orthogonal Decomposition (SPOD), the research examines how cavity-induced instabilities, such as Rossiter (acoustic feedback-driven) and centrifugal modes, interact to drive transition, building on prior work linking surface imperfections to bypass transition mechanisms. Results reveal nonlinear couplings between these modes, with Rossiter modes persisting into turbulent regions and centrifugal instabilities introducing three-dimensional flow distortions, highlighting their combined role in destabilizing the boundary layer.