A wind-tunnel experiment on real-time opposition control of turbulence

Real-time, opposition control of near-wall turbulence has been carried out in physical experiments by selectively canceling the downwash of high-speed fluid during the sweep events. The control strategy that we employed in this study was a combination of in-phase u-velocity and out-of-phase v-velocity control, where the wall-ward advancement of sweep events with positive u and negative v velocity was blocked by wall-normal jets. Changes made to the sequence of sweep events by opposition control in the near-wall region of turbulent boundary layer were examined using hot-wire measurement with conditional sampling technique. (C) 2006 American Institute of Physics.