STUDY ON GENERATION MECHANISM OF INNER SECONDARY FLOW IN A CORNER FORMED BY A VERTICAL WALL AND A FREE SURFACE

A fully-developed turbulent open-channel flow was computed to clarify the generation mechanism of inner secondary flow in a mixed-boundary corner formed by a vertical wall and a free surface using direct numerical simulation (DNS). The Reynolds number for the simulations was Reτ=150 and the aspect ratio of channel width to flow depth was 2. Stable secondary currents and the maximum-velocity-diphenomena were reasonably reproduced. The significant results were the identification of inner secondary flow which rotates toward the wall at the free surface and down away from the surface along the wall. Then, in this paper, the Reynolds momentum equations were analyzed to discuss the generation mechanism. Detailed evaluation of Reynolds stress terms and pressure terms revealed that the imbalance between them causes the inner secondary flow.