MECHANISM OF DRAG REDUCTION BY SPANWISE WALL OSCILLATION IN TURBULENT CHANNEL FLOW
壁面展向周期振动的槽道湍流减阻机理的研究

An investigation into a turbulent channel flow subjected to spanwise wall oscillation is carried out via direct numerical simulation. By wall oscillation, turbulence is suppressed and friction drag is reduced. The transportation of Reynolds stresses under the influence of the oscillating wall is analyzed at the initial and statistically stationary stages to further disclose the mechanism of turbulence suppression and drag reduction. It is found that the moving wall can cause the transient growth of spanwise velocity fluctuations only at the very beginning of wall oscillation and thereafter the pressure-strain terms play an important role. The attenuation of turbulence intensities and skin friction at the statistically stationary stage is mainly due to the sustained reduction of the pressure-strain terms.