Mean flow and turbulent statistics of the flow over a submerged sharp-crested weir

Flow over a sharp-crested weir shows the free flow, for which the critical flow occurs at the tip of the weir. However, during the high flow, the downstream water level affects the overflow and the flow over the weir becomes the submerged flow. The submerged flow exhibits four different flow regimes depending on the downstream water level, namely impinging jet, surface jump (or breaking wave), surface wave, and surface jet. In this paper, the four flow regimes of the submerged flows over the sharp-crested weir are simulated using large eddy simulation (LES). The flow condition comes from the laboratory experiment by Rajaratnam and Muralidhar (1969), and the computed results are validated against experimental data of the surface jet. For the same discharge, the impinging jet, surface jump, and surface wave are made by changing the ratio of the tailwater depth and the head above the weir crest. Characteristics of the free surface fluctuations, and mean flow and turbulence statistics of the four flow regimes are investigated. LES results indicate that the four flow regimes show distinctive characteristics of the recirculation zones downstream of the weir and the free surface. Their impact on the bed downstream of the weir is also examined.