Effect of the parameters of traveling waves created by blowing and suction on the relaminarization phenomena in fully developed turbulent channel flow

A series of direct numerical simulations of a fully developed turbulent channel flow controlled by traveling waves induced by blowing and suction is performed. Relaminarization, i.e., the transition from turbulent flow to laminar flow, is observed for some sets of parameter when the wave is traveling in the downstream direction. Since the downstream traveling wave produces the drag, the drag of the flow is slightly larger than the corresponding laminar flow. A parametric study is performed, and reveals that the range of control parameters that produce relaminarization are the wave speed and amplitude of the wave which scale with the mean bulk flow rate corresponding to laminar flow and the wavelength which scales with the viscous scale. When relaminarization occurs, the amplitude of the wave, wavelength, and wave speed are in the range of a/(u) over bar (lam) > 0.1, 200 < lambda(+) < 500, and c/(u) over bar (lam) > 1.5, respectively. These ranges are organized by displacement thickness and are between 3 and 10 wall units when the relaminarization occurs. A three-component decomposition is used to observe the effects of the control parameters. The periodic component has the effect of decreasing the random component, resulting in relaminarization. When the displacement thickness is smaller, the periodic component does not have the effect of decreasing the random component, and the drag is virtually unchanged. When the displacement thickness is larger, the periodic component produces large drag, and the drag increases despite the decrease in the random component. (C) 2014 AIP Publishing LLC.