Abstract
Fully developed three-dimensional turbulent flow over sand ribbons in an open-channel is computed to clarify the generation mechanism of secondary currents of the second kind by direct numerical simulation (DNS) using a regular grid under a generalized curvilinear coordinate system. Stable secondary currents and turbulent characteristics are reasonably reproduced. Detailed evaluation of each term in a mean vorticity transport equation revealed that the secondary currents of the second kind is generated principally by cross-planar turbulent shear stress and that the anisotropy of the cross-planar turbulent normal stresses restrains the generation of the secondary currents.
