It is often of interest to control flow development to improve system performance or avoid undesired effects such as vibrations or noise. We investigate passive control strategies, such as surface modifications, and various types of active flow control, including acoustic emissions, embedded synthetic jets, and surface mounted plasma actuators Video 2 is an example of how periodic acoustic excitation can significantly change flow development over an airfoil.
Here, a specific frequency was carefully selected to stimulate transition to turbulence. Because of this, the shear layer rolls up into vortices earlier in the excited flow, which causes the flow to reattach earlier and reduces the size of the separation bubble.
Video 2a.
Video 2b.
Video 2. Flow control with periodic excitation.