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Dissolved Oxygen Variation on the Steps with a Quarter Circle End Sill for Flows over the Stepped Spillways

Determining the aeration efficiency of the stepped spillways is important because the Dissolved Oxygen (DO) concentration helps indicate the water quality. This study investigated the effects of varying step shape and chute slope on the aeration efficiency for stepped spillways. The measured parameters were DO, the inception point of the free surface, and the water surface profile above the crest to evaluate the geometry variation impacts. Several experiments were conducted on a six-step configuration over a stepped spillway with chute angle (θ = 26.6°, 21.8°, and 8.9°). The discharges up to 0.055 m3/s. The step configurations were including flat step, normal end sill, and quarter circle end sill. The results showed when the chute angle changed from 26.6° to 8.9°, the aeration efficiency of E20 improved with 11.51% at the lowest discharge and 6.05% at the highest discharge for the flat step model with 10 steps. Also, E20 improved 11.39% at the lowest discharge and 6.50% at the highest discharge for the flat step model with 6 steps. The performance of the steps with the quarter circle end sill model in terms of aeration efficiency increased by 10%.