Direct numerical simulation of turbulent Taylor-Couette flow controlled by a traveling wave-like blowing and suction for drag reduction.

Flow control to decrease the skin-friction drag in wall turbulence is important in engineering viewpoints. Recently, a traveling wave-like control is known to not only decrease the skin-friction drag, but also induce relaminarization phenomenon in the turbulence channel flow. Therefore, it is worth to investigate the control effect in other canonical flows. In this study, we investigated the drag reduction of a traveling wave-like control in fully developed turbulent Taylor-Couette flow using direct numerical simulations. The Reynolds number based on the rotating velocity of the inner wall and the radius of the centerline was set to be 84000. We imposed a traveling wave-like control only in the inner wall and investigated the control effect parametrically. We found that this control resulted in 30{\%} drag reduction when the wave traveled in the same direction as the rotation of the inner wall and faster than the rotation. In this presentation, we will discuss the drag reduction mechanisms comparing with the other control techniques such as an opposition control.