Abstract
We investigate numerically self-sustained oscillating flows over open cavities. The two-dimensional incompressible Navier-Stokes equations are solved using finite difference method. A series of simulations are performed for a variety of cavity length from 1.0 to 3.8 at 0.1 interval. The results show mode switchings among no oscillations, mode II, mode III and wake mode oscillations. The Strouhal number variation is consistent with experimental data. The results of flow fields in the cavity reveal the relationship between the cavity shear layer oscillation modes and recirculating vortices in the cavity. The self-sustained oscillations start when number of recirculating vortices become two. The mode switching form mode II to mode III occurs when number of vortices change from three to four. The wake mode oscillation is similar to that of other experimental and numerical investigations.
