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.
Highlights
A stepped spillway is an important hydraulic structure widely used in hydraulic projects owing to its high energy dissipation function
The results showed that energy dissipation in the pooled stepped spillway is air concentration is larger than that in the flat stepped spillway
All the stepped spillway predict the location of the inception point in the stepped spillways
Summary
A stepped spillway is an important hydraulic structure widely used in hydraulic projects owing to its high energy dissipation function. Due to the increase of the energy dissipation rate, the stilling basin at the toe of the dam requires less size than that of a smooth spillway [1,2]. Aeration is a process in which air enters the surface of a spillway. The spillway may be subjected to cavitation damage. Aeration is necessary to prevent cavitation damage in stepped spillways. Air entrainment starts when the turbulent boundary layer coincides with the water depth. The point at which air entrainment starts is called the inception point, i.e., the location where a non-aerated flow zone is converted into an aerated flow zone [3,4]
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