SUPPRESSION OF TURBULENCE IN WALL-BOUNDED FLOWS BY HIGH-FREQUENCY SPANWISE OSCILLATIONS

The response of wall-flow turbulence to high-frequency spanwise oscillations was investigated by direct numerical simulations of a planar channel flow subjected either to an oscillatory spanwise cross-flow or to the spanwise oscillatory motion of a channel wall. Periods of oscillation, T(osc)+ = T(osc)u(tau)2/nu, ranging from 25 to 500 were studied. For 25 less-than-or-equal-to T(osc)+ less-than-or-equal-to 200 the turbulent bursting process was suppressed, leading to sustained reductions of 10% to 40% in the turbulent drag and comparable attenuations in all three components of turbulence intensities as well as the turbulent Reynolds shear stress. Oscillations at T(osc)+ = 100 produced the most effective suppression of turbulence. The results were independent of whether the oscillations were generated by a cross-flow or by the motion of a channel wall. In the latter case, suppression of turbulence was restricted to the oscillating wall while the flow at the other wall remained fully turbulent. Spanwise oscillations may provide a simple and effective method for control of turbulence in wall-bounded flows.