Direct numerical simulation of dissimilarity effect by traveling wave-like body force control in turbulent channel flow

For energy efficiency, flow control techniques for the skin-friction drag and the heat transfer in a wall-turbulence are essential issues. Due to the strong analogy between momentum and heat transfers, it is difficult to obtain the simultaneous achievement of the skin-friction drag reduction and heat transfer enhancement. The control, which achieves simultaneous reduction of frictional resistance and enhancement of heat transfer, is called as dissimilarity control. In this study, we perform direct numerical simulations of the turbulent channel flows controlled by the traveling wave-like body force. The traveling wave control mimics the self-excited thin film in the corresponding experimental study. When the wave travels slower than the mean bulk velocity in the downstream direction, we found increase of the skin-friction drag, the heat transfer, and the analogy factor. The vortical structures are significantly promoted and increased. In addition, the results of the parametric study imply that the upstream traveling wave has a potential to induce the dissimilar control effect, i.e., reduction of the skin-friction drag and enhancement of the heat transfer.