Opposition Control of Near-Wall Turbulence With a Piston Type Actuator

Abstract

Opposition control of near-wall turbulence was carried out using a wall-normal jet from a piston-type actuator, by selectively canceling the downwash of high-momentum fluid during the sweep events. By employing an innovative methodology we were able to study the effectiveness of the scheme without carrying out real-time control, overcoming experimental difficulties associated with the high frequency responses required for the turbulence control. Observed changes of the burst signature in the turbulent boundary layer suggest that there is a possibility of reducing the skin-friction drag when opposition control is carried out with appropriate timing.