Direct numerical simulation of low Reynolds number flows in an open-channel with sidewalls
A direct numerical simulation of low Reynolds number turbulent flow in an open-channel with sidewalls is presented. Mean flow and turbulence structures are described and compared with both simulated and measured data available from the literature. The simulation results show that secondary flows are generated near the walls and Prey surface. In particular, at the upper corner of the channel, a small vortex called inner secondary flows is simulated. The results Show that the inner secondary flows, counter-rotating to outer secondary flows away from the sidewall increase the shear velocity near the free surface. The secondary flows observed in turbulent open-channel flows are related to the production of Reynolds shear stress. A quadrant analysis shows that sweeps tend ejections tire dominant in the regions where secondary flows rush in toward the wall and eject from the wall respectively. A conditional quadrant analysis also reveals that the production of Reynolds shear stress and the secondary flow patterns are determined by the directional tendency of the dominant coherent structures. Copyright (C) 2009 John Wiley & Sons, Ltd.
direct numerical simulation sidewall secondary flows open-channel flows quadrant analysis coherent structures