Numerical Simulation of Hydraulic Characteristics of Spillway Tunnel with Gradually Expanding Outlet and Lower outlet height

Using a practical and efficient overall three-dimensional turbulent numerical model of the spillway tunnel, the numerical simulation of the hydraulic characteristics of the spillway tunnel with the gradually expanding outlet and lower outlet height is carried out. The calculation results show that when the gate is fully open, there is pressure flow in the whole tunnel of the spillway tunnel, and the flow state is stable; when the gate is not fully open and the water level is low, the flow state in the tunnel is unstable, and the free and pressure flow occur alternately. When the gate is at a small opening, the flip bucket raises the water level at the outlet, and the lower outlet height causes insufficient air supply in the cave, which is prone to cavitation. The lift distance is small, and it is easy to scour the slope of the hole. The lower outlet height at the outlet of the spillway tunnel further exacerbates the complexity of the hydraulic characteristics in the back arc section, which should be paid attention to during design and construction, and it is necessary to carry out hydraulic model test research.