抄録
A fully-developed turbulent open-channel flow was computed to investigate the large scale coherent vortex structures in both a solid-boundary corner and a mixed-boundary one using direct numerical simulation (DNS) where the former was formed by a vertical wall and a river bed, and the latter formed by a verticalsolid wall and a horizontal free surface. The Reynolds number for the simulations was Reτ=150 and the aspect ratio of channel width to flow depth was 2.The results showed that stable secondary currents and the maximum-velocity-dip phenomena were reasonably reproduced.The coherent vortex structures were also examined using flow visualization techniques based on cylindrical vortex tubes. The most significant results were the identification of inner secondary flow in the mixed-boundary corner which rotates toward the wall at the free surface and down away from the surface along the wall.
