Vortex simulation of leading-edge separation bubble with local forcing

A numerical study is made of the flow control of leading-edge separation bubbles in a two-dimensional semi-infinite blunt plate, which is aligned parallel to the main stream. A version of the discrete-vortex method is utilized. A time-dependent point source of small magnitude is introduced near the separation edge. The effect of local source forcing on the evolution of a leading-edge separation bubble is scrutinized by varying the strength and the forcing frequency of the source. It is found that the reattachment length attains a single minimum at lower forcing levels, while it shows double minima at moderately high forcing levels. Based on the numerical results, the mechanism of decreasing reattachment length is pursued. These findings are qualitatively consistent with the existing experimental results for a blunt circular cylinder.