Experimental study of closed loop control of cross-flow instability driven transition by plasma actuator

A closed-loop control was implemented to mitigate stationary cross-flow instability vortices in the boundary layer of a swept wing. Control was achieved using a multichannel plasma actuator and a flow velocity sensor based on a particle image velocimetry system. The optimal control strategy was determined using a gradient descent method, which minimized the root mean square of the steady velocity modulation. The excitation of the boundary layer by a single section of barrier discharge was investigated, with key actuator characteristics, such as linearity limits and noise levels, measured during the experiment. The system's performance was evaluated in a wind tunnel experiment, with various roughness patterns used to force the initial vortices. For isolated roughness elements, substantial transition delay was achieved.