Study on the Energy Dissipater Type of Diversion Tunnel Outlet under Condition of the Large Flow and Large Intersection Angle

The problem of energy dissipation at the diversion tunnel outlet of large hydropower station is prominent. Because its outflow is centralized, which is easy to scour the riverbed and impact the riverbank, especially under the conditions of large flow and large angle of intersection. Based on RM hydropower station, this paper studies the impact of different types of energy dissipater of the diversion tunnel outlet by hydraulic model test. The results show that: (1) the diversion tunnel outlet set energy dissipater, such as baffle block, trapezoidal continuous retaining wall, slotted gearing sill, can greatly reduce the frictional velocity, change the unfavorable velocity distribution of “large at the bottom, small at the surface”, and reduce the uniformity coefficient of velocity in the cross section at the interface with the downstream channel to varying degrees; and (2) when the height ratio of the gearing sill of slotted energy dissipator is about 0.1~0.3, the energy dissipation effect is relatively better, and the maximum fluctuating pressure on the opposite bank and the banked-up water level are greatly reduced.