VORTEX SIMULATION OF LEADING-EDGE SEPARATION BUBBLE WITH LOCAL FORCING

A numerical study is made of the flow control of leading-edge separati on bubbles in a two-dimensional semi-infinite blunt plate, which is al igned parallel to the main stream. A version of the discrete-vortex me thod is utilized. A time-dependent point source of small magnitude is introduced near the separation edge. The effect of local source forcin g 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 forcin g levels. Based on the numerical results, the mechanism of decreasing reattachment length is pursued. These findings are qualitatively consi stent with the existing experimental results for a blunt circular cyli nder.