要約

Reduction of skin-friction drag in a channel flow by traveling wave-like surface heating/cooling is investigated by means of linear analysis and direct numerical simulation. The linear analysis reveals that a downstream traveling wave can reduce the skin-friction drag. Due to non-quadrature between the streamwise and the wall-normal velocity disturbances induced by the buoyancy force, negative Reynolds shear stress is created in the regions near the walls, which contributes to the skin-friction drag reduction. The direct numerical simulation shows that a traveling wave at a high wavenumber slightly reduces the friction drag in a fully developed turbulent channel flow. The velocity fluctuations and the Reynolds shear stress are slightly attenuated by this control. The friction drag increases for larger magnitudes and lower wavenumbers of the traveling waves. Non-zero mean temperature profile is created due to the turbulent heat flux induced by the control.