104 / 2024-01-30 11:56:59

Characteristics of tailrace channel flow and appropriate location of fish-gathering system inlet

Tailrace channel flow,Fish-gathering system,Submerged wall jet

Fishway or fish-gathering system inlet is often built at tailrace channel, where fish usually gather, attracted by water turbine outflow. However, flow in the tailrace channel is very complex and strongly three-dimensional, due to various turbine operation conditions and irregular bed and bank topography. This paper aims to propose proper location of fish-gathering system inlet based on flow pattern, flow velocity distribution and fish swimming speed. A 3-D numerical flow model including three draft tubes and tailrace channel was built initially. Then tailrace channel flow with different water level and draft tube flow conditions was calculated. Finally, the paper analyzes characteristics and velocity distribution of tailrace channel flow. The draft tube flow into tailrace channel is a rectangular submerged wall jet above slopes and its velocity evolution confirms to basic wall jet law. Obviously, the jet length is longer with larger draft tube outflow velocity. With the same draft tube outflow velocity, the jet under larger water level is also with larger velocity reduction speed. The reason is that the jet under larger water level exchanges more energy with its adjacent static water. Also, the jet route, jet length and jet velocity variation is affected by its nearby jets. The jets produced both vertical and horizontal vortex in adjacent fluids. The end of the adverse slope downstream of the tailrace channel is judged to be the appropriate location of fish-gathering system inlet.