Reynolds number dependence of flow past a shallow open cavity

Measurements were carried out in a shallow open cavity with particle image velocimetry technique. The cavity has a length- to-depth ratio of 4:1, and the upstream inflow conditions include laminar, transient, and turbulent regimes at seven different Reynolds numbers. The measured instantaneous velocities were analyzed through ensemble average, vortex extraction, and proper orthogonal decomposition (POD) to investigate overall flow circulations, Reynolds stress distribution, spanwise vortex population, and the characteristics of the POD modes. The results reveal distinctive Reynolds number dependence of the cavity flow, e.g. an increase in Reynolds number results in constant migration of the overall circulation, enhancement of Reynolds stress, reduction of correlation between vortex and Reynolds stress, and decrease of fractional energy of the characteristic POD modes. Finally, a phenomenological model was proposed to describe various features of cavity flow.