A dynamic mode decomposition of the saturation process in the open cavity flow

The flow over the incompressible open cavity has been studied both numerically and experimentally in previous works by the authors [6], [16]. In these studies the in-depth linear stability analysis of the problem provided a detailed description of the flow features in the linear regime, where span-wise periodic perturbations over a steady two-dimensional flow were studied. The experiments conducted in said work, with span-wise walls, show the flow in a saturated state. The main structures that appear in the flow were identified as three-dimensional centrifugal modes. Even if the flow conditions for these two approaches are different, common features appear in both: the spatial structure of the modes in the saturated regime according to the experiments is the one predicted by linear analysis, but there is a shift in frequencies for the oscillating modes. The present work uses a three-dimensional non-steady direct numerical simulation (DNS) with periodic span-wise conditions to study the effect of saturation. In order to analyze the DNS results a Dynamic Mode Decomposition (DMD) was used.