Experimental Study on the Separation Control of Turbulent Boundary Layers by Vortex Excitation

Artificial disturbances are introduced to a turbulent boundary layer separating at a convex corner to see how excited vortices control the turbulent separation. The results clearly show that excitation of vortices with appropriate scale can effectively suppress the separation of turbulent boundary layer, not unlike the case of laminar separation. However, strong disturbance growth due to Kelvin-Helmholtz instability, which decisively dominates development of separation bubble for laminar separation, does not occur for turbulent separation. Therefore direct excitation of energetic vortices around the separation point is required for suppression of turbulent separation.