Experimental study of the air concentration diffusion in aerated chute flows downstream of lateral and bottom aerators

Flow aeration is an effective way to protect the chute structure from cavitation erosion damage, and various chute aerators are applied for high-velocity and large discharge flows. The aeration protection for the chute floor and sidewall is mainly affected by aerator designs and air diffusion properties. However, detailed comparisons of air concentration distributions generated by different chute aerator types are limited. In this paper, physical model tests are conducted to measure and compare the air diffusions generated by different chute aerators, including the bottom aerator, the lateral aerator, and the full-section aerator. A clear-water zone in the middle of the water flow easily appears for the bottom aerator, and the air concentration in the zone near the bottom plate decays faster downstream. The lateral aerators can effectively improve the aeration protection of the sidewall in the middle of the water flow, but due to the influence of water fins, a prominent clear-water zone appears near the bottom plate of the sidewall, which cannot be eliminated downstream. The full-section aerator composed of the bottom aerator and lateral aerator can generate a fully aerated flow and eliminate clear-water effects. In addition, the air diffusion generated by the full-section aerator near the chute bottom and sidewalls increases and stably develops downstream. Test results indicate that compared to isolated bottom and lateral aerators, the full-section chute aerator can obtain acceptable air concentration distributions and near-wall air diffusions for cavitation erosion protection of high-velocity chute flows.