Effects of arbitrary directional system rotation on turbulent channel flow

Abstract

A series of direct numerical simulations is carried out to study the effects of system rotation on a fully developed turbulent channel flow. The rotating axis is in an arbitrary direction to the channel walls. Three cases are considered by combining two of the orthogonal rotating vectors, i.e., streamwise, wall-normal, and spanwise rotations. The spanwise rotation effect is still dominant even when another orthogonal rotation is imposed to the system. However, the streamwise rotation induces the recovery of turbulence on the suction side, the enhancement of the secondary flow rotating in the positive streamwise direction, and the redirection of the near-wall vortical structures if this rotation is much stronger than the spanwise rotation. The wall-normal rotation reduces the slope of the linear region of the streamwise mean velocity distribution and increases the streamwise friction coefficient. In the case of combined streamwise and wall-normal rotation, turbulence is also enhanced on one side and depressed on the other side, while rotation-induced large-scale vortices also appear, extending in the absolute mean flow direction, even though no explicit spanwise rotation is imposed to the system.