Abstract: The roughness of annular corrugated steel pipe fishway could generate sufficiently low flow velocities near the boundary, which facilitates fishes to immigrate towards the upstream. In this paper, the water surface line, flow velocity field, and turbulent flow field in the annular corrugated steel pipe culvert fishway are simulated under different conditions (flow rate 0.05 m3/s, 0.07 m3/s and 0.09 m3/s, embedded depth 0D, 0.1D and 0.2D, and slope gradient 0.4%). Results show that high velocity field (dimensionless velocity greater than 0.9) is located in the central area of the cross section of the culvert, and high turbulent flow field (turbulence intensity greater than 0.2) is located near the central area of the water surface. In large areas near the side walls of culvert bottom, due to relatively low velocity, the turbulence intensity is relatively low (less than 0.1) and fishes could complete migration using this passage. Compared with nonembedded culverts, the embedded culvert has lower average velocity and gentle variation of turbulence intensity, therefore it is more conducive to fish migration.

Key words: numerical simulation, hydraulic characteristics, fishway, corrugated steel pipe culvert, roughness, high velocity field, high turbulent flow field