Numerical Simulation of Water and Sediment near the Normal Funnel.

The sediment-carrying capacity is reduced due to the rise of water level and the reduction of velocity, which leads to sedimentation in the reservoir, especially in front of the dam. Therefore, the storage capacity, flood control ability, and power generation are reduced, which affects reservoir functions and economic efficiency owing to reservoir sedimentation. The main measures to solve the problem of reservoir sedimentation include dredging in reservoir, reducing inflow sediment realized by soil protection and vegetation, as well as reservoir operation management such as "storing clear water and discharging muddy flow", and sediment discharging by heterogeneous flow, etc. In this paper, a normal funnel device with the smooth surface that has arbitrary order derivative is designed for discharging sediment in reservoir. The Euler two-phase flow near the normal funnel is numerically simulated with the Realizable k-e turbulence model on rectangle and O-type grids. Numerical model is tested by data on experiment flow that carried out in flume. The flow velocities, vorticities and sediment phase concentrations are analyzed under different boundary conditions. Research shows that velocity gradient is large in normal funnel, and phase concentration contours display the V-shaped asymmetrical distribution. Three large vorticity areas appear in the front edge, the left and right rear sides of the normal funnel. The large flow velocities and small resistance appear near the wall of the normal funnel. The average sediment concentrations at the output of the normal funnel are 0.462, 0.521 and 0.558 under three boundary conditions. The average vorticity is reduced by 25.8%-27.2%, the efficiency of discharging sediment remarkably increases with 15.2%-16.5% in contrast to the cone funnel. It demonstrates that the normal funnel is more favorable than the cone to smoothing flow, reducing energy dissipation, enhancing the capacity of sediment transport and discharging sediment outwards reservoir. [ABSTRACT FROM AUTHOR]