Abstract:

The finite difference method （FDM） is applied in the present paper to solving the unsteady N-S equations for incompressible fluids. ADI and SLOR methods are served for the vorticity equation and the Poisson equation for , respectively. The upwind scheme is used for the convective terms in order to speed up the convergence. The moving boundary conditions are specially treated, and the effects of outlet conditions on the flow field are also examined. Numerical results obtained show the followingss The spoiler's oscillation induces forming, growing and shedding of vortices. The shedding frequency of vortices is equal to that of the spoiler's oscillation. The growing and shedding of vortices. The shedding frequency of vortices is equal to that of the spoiler's oscillation. The forced unsteady separated flows under the present investigation depend mainly on the reduced frequencies, At low reduced frequencies, the vortices shed from the spoiler interact weakly, with each other, and move downstream with an almost uniform speed of 0.38V∞. At high reduced frequencies, the interaction between the adjacent vortices strengthens. They close to and rotate around each other, and eventually, merge into a single vortex.

Key words: N-S equations, spoilers, unsteady flow, separated numerical calculation