Effect of height and geometry of stepped spillway on inception point location

Abstract

Air entrainment in a stepped spillway is very important to protect the spillway from cavitation damage. The inception point is the location where air starts entering the non-aerated flow zone. The inception point location depends on different parameters, such as the discharge, step height, and step shape. In this paper, various stepped spillways, including flat steps, pooled steps, and round steps with different step heights were numerically simulated using the volume of fluid and realizable k-ε models. The results indicate that the inception point location moves downwards with the increase of the discharge of the stepped spillways. The length of the non-aerated flow zone increases with the discharge. The inception point location moves downwards as the step height decreases and the step number increases at the same discharge. The inception point location of the round stepped spillway model is much closer to the spillway crest than that of the flat stepped spillway with the same number of steps. The inception point location of the pooled stepped spillway is closer to the spillway crest than that of the flat stepped spillway, but more downstream than that of the round stepped spillway.