高レイノルズ数乱流における正方形ダクト二次流れ

Abstract

Using an efficient spectral method, we perform direct numerical simulation of turbulent square-duct flow at high Reynolds numbers to investigate the dependence of turbulent secondary flow on the Reynolds number. Similar to previous studies, our simulation also shows that the intensity of the secondary flow can be most likely scaled by the bulk mean velocity. We further investigate the distribution of Reynolds stress terms in the averaged equations of the cross-streamwise velocity, which is the cross-streamwise driving force of the secondary flow to find that the driving force is oriented to the corner and its curl (driving torque) is localized in the corner region as the Reynolds number increases. The distribution of the driving force is observed to scale with the kinematic viscosity and the friction velocity. These results suggest that the secondary flow of the order of the friction velocity is induced near the corners. We also discuss a possibility that the intensity of the whole secondary flow may be scaled by the friction velocity.