Active cancellation of artificially introduced Tollmien–Schlichting waves using plasma actuators

In the present work artificially excited Tollmien–Schlichting (TS) waves were cancelled using plasma actuators operated in pulsed mode. In order to achieve this a vibrating surface driven by an electromagnetic turbulator was flush mounted in a flat plate to excite the TS waves. These were amplified by an adverse pressure gradient induced by an insert on the upper wall of the test section. A control plasma actuator positioned downstream of the excitation actuator attenuates the waves by imparting an unsteady force into the boundary layer to counteract the oscillation. As a result the amplitude of the velocity fluctuations at the excitation frequency is reduced significantly depending on the distance from the wall. A parameter study was performed to identify the influence of several operation parameters of the control actuator.