Numerical Simulations of Two-Dimensional Incompressible Flows Over Cavities and Their Control

We investigate numerically self-sustained oscillating flows over open cavities. The incompressible Navier-Stokes equations are solved using finite difference method for two-dimensional cavities with an upstream laminar boundary layer. A series of simulations are performed for a variety of cavity length to depth ratio. The results show mode switchings among nonoscillations, mode II and mode III oscillations. Variation of Strouhal number is in good agreement with available 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. We also demonstrate that oscillations are suppressed by our control method using moving bottom wall.