Vortex Identification Study of a Turbulent Cavity Flow

A combined vortex identification and Proper Orthogonal Decomposition (POD) analysis is applied to high-resolution Particle Image Velocimetry (PIV) measurements of a turbulent flow past an open shallow cavity. The PIV measurements, at a cavity depth based Reynolds number of 42,000, capture the flow structure and turbulence, upstream, over, and downstream an open cavity having a length-to-depth ratio of four. Vorticity and second invariant Q of the velocity gradient tensor analysis are used to identify the vortical structures and the overall flow field features. POD analysis is applied to the vorticity and Q fields to identify the most energetic vortical structures and flow features. The results demonstrate the superiority of the combined Q-criterion and POD analysis in identifying distinct vortical structures and their evolution.