DIRECT NUMERICAL SIMULATION OF SECONDARY CURRENTS AND VORTEX STRUCTURES IN AN OPEN CHANNEL FLOW

Direct Numerical Simulation of turbulent flow in an open channel was carried out. The Reynolds number for the simulations was Reτ=150 and the aspect ratio was 2. The coherent vortex structures were also examined using visualization techniques. 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. and the basic structure consisting of a pair of secondary flows in a corner occurs not only in solid corner but also in free surface corner. Then, detailed evaluation of Reynolds stress terms and pressure terms of the momentum equations revealed that the imbalance between them causes the inner secondary flow.