Flat and Pooled Stepped Spillways for Overflow Weirs and Embankments: Cavity Flow Processes, Flow Aeration and Energy Dissipation

For overflow weirs and embankments, the stepped chute profile may increase the rate of energy dissipation on the waterway. Herein four different stepped chute configurations were tested with a focus on the cavity flow processes, flow aeration and energy dissipation performances. Detailed flow visualisations and air-water flow measurements were conducted for all configurations. The results highlighted the strong flow aeration. The residual energy was the lowest for the flat stepped weir. The data for the stepped spillway configuration with in-line and staggered configurations of flat and pooled steps showed large differences in terms of residual head in the transverse direction consistent with the threedimensional flow motion. The in-line and staggered configurations did not provide any advantageous performances in terms of energy dissipation and flow aeration, and they were affected by three-dimensional patterns leading to some flow concentration.