Wedge Aerator at the Bottom Outlet in Flat Tunnels

Aerators are applied to provide air entrainment and cavitation erosion protections for high-speed flows. By traditional chute aerators in high-head bottom tunnels, it is difficult to maintain effective aeration protection for low-Froude-number and small-slope conditions. The present study explores a wedge aerator design at the bottom outlet, and detailed experimental data on the aeration cavity and the entrained air diffusion were obtained to assess the aeration protection performance. The wedge aerator separates the water flow from the bottom outlet into an upper free jet and a lower flow layer, creating a middle aeration cavity. The flowing lower layer can enhance the aeration cavity stability, ensuring the cross-sectional air diffusion generation downstream due to the flow collision interactions. The flow Froude number and vertical location are the main parameters affecting the air entrainment coefficient, cross-sectional air concentration distribution, and sufficient concentrations close to the chute floor. Optimized wedge aerators are proposed, indicating that the flow interior separation is an effective hydraulic design for bottom outlets in hydraulic engineering.