Numerical Simulation Study on a Novel Spanwise Oscillating Wall Drag Reduction Method

Spanwise wall oscillation is widely recognized as an effective active technique for turbulent drag reduction. In this study, a segmented spanwise wall oscillation (SSW) strategy is proposed, in which the wall is divided into several streamwise segments and adjacent segments oscillate in opposite spanwise directions. This configuration not only enhances the drag reduction performance of conventional spanwise oscillation but also enables self-balancing of driving forces through the counter-directional motion of neighboring segments. Direct numerical simulations (DNS) of turbulent channel flow at Re_τ = 200 are performed to systematically investigate the drag reduction characteristics of the segmented configuration. The wall is divided into four, eight, and sixteen streamwise segments, and simulations are conducted at an oscillation amplitude of A + = 12 over a range of oscillation periods T⁺ = 50–200. The results show that the segmented oscillation configuration can achieve higher drag reduction rates than the conventional oscillating wall. The optimal drag reduction increases with the number of segments, indicating that the segmentation pattern significantly influences the control performance. Flow structure analysis suggests that the reverse oscillation of adjacent segments generates localized disturbances at the interfaces, which modifies the spatial distribution of streamwise vortices and induces a characteristic bending of near-wall streaks. These structural modifications are associated with a redistribution of vorticity and a reduction in turbulent kinetic energy production, while the increase in dissipation remains relatively limited. Overall, the segmented oscillation strategy provides an effective approach for modulating near-wall turbulence structures and improving drag reduction performance, while offering potential advantages for practical implementation due to its force self-balancing characteristics.