Herein is introduced the mechanism for active control influencing the generation of the near-wall streamwise vortices, which are closely related to the production of high skin friction in wall-bounded turbulent flows. A new opposition control scheme with adjusting control amplitude is proposed and evaluated in turbulent channel flow by direct numerical simulations. The maximum drag reduction rate can be greatly enhanced by the strengthened control. Finally the effectiveness of the control to the coherent structures at high Reynolds numbers is investigated by using a linear transient growth model.
Bibliographical noteFunding Information:
This work was supported by the National Natural Science Foundation of China (Grant Nos. 10925210 and 11132005).
- active control
- coherent structure
- drag reduction
- wall turbulence