Investigation of turbulent flows using spillway models aiming to aid downstream migration of fish
Ali Shirinzad, Sedem Kumahor, Mark F. Tachie, Haitham Ghamry, Christos Katopodis
Abstract
Abstract Dams and other flow control structures constitute obstacles to upstream and downstream aquatic habitats, reducing life‐cycle success and even eliminating diadromous and potamodromous fish species from river basins. Providing effective passage past hydroelectric dams is critical for restoring habitat connectivity and sustaining populations of fish species. Surface water release over spillways is effective in diverting fish from turbines and establishing a safe bypass for downstream migrants. Developing an effective passage system over spillways requires both biological knowledge of fish behavior and abilities, as well as hydraulic knowledge of spillway flows to provide hydrodynamic conditions that fish may exploit. The present study experimentally investigates several depths, velocity, and turbulence fields intended to promote the downstream migration of fish over spillways. Instantaneous velocity fields were measured in an open recirculating rectangular water channel. A 90° standard spillway model, as well as a spillway model with a modified upstream face slope of 45°, were tested for two water depths. The results show the presence of a distinct recirculation bubble at the heel of the 90° standard spillway with the shallower water depth. It was concluded that the upstream recirculation bubble may be suppressed by either increasing the water depth or decreasing the upstream face slope. Decreasing the upstream face slope also resulted in a more uniform distribution of acceleration and lower turbulence along the upstream face of the spillway. The modified spillways provide more suitable hydrodynamic conditions for downstream migrants.