Stepped Spillways and Energy Dissipation: A Non-Uniform Step Length Approach

Abdelwanees Ashoor,Amin Riazi

doi:10.3390/app9235071

Abstract

A stepped spillway, which is defined as a spillway with steps on the chute, can be used to improve the energy dissipation of descending water. Although uniform stepped spillways have been studied comprehensively, non-uniform stepped spillways need more attention. In the interest of maximum energy dissipation, in this study, non-uniform stepped spillways were investigated numerically. To this end, within the range of skimming flow, four different types of non-uniform step lengths, including convex, concave, random, and semi-uniform configurations, were tested in InterFOAM. To evaluate the influence of non-uniform step lengths on energy dissipation, the height and number of steps in all models were fixed and equal to a constant number. The results indicated that in semi-uniform stepped spillways, when the ratio between the lengths of the successive steps is 1:3, a vortex interference region occurs within the two adjacent cavities of the entire stepped chute, and as a result, the energy dissipation increases by up to 20%.

Highlights

To prevent overtopping and possible failure of a dam, excess water in reservoirs is released by spillways
The results revealed that the realizable k-ε model is the most efficient
It was observed that the rate of energy dissipation increases slightly when the spillway slope decreases, and this has an inverse relationship with the discharge (Figure 10)

Summary

Introduction

To prevent overtopping and possible failure of a dam, excess water in reservoirs is released by spillways. A stepped spillway has a profile made up of steps on the chute, which increases the energy dissipation and in turn helps to reduce the required size of the stilling basin. The energy dissipation occurs by flow recirculation, with or without air entrainment, under the pseudo-bottom caused by the flow on each step [6,7]. Another important feature of stepped spillways is, because of the high turbulence of the flow and the absorbed air from the atmosphere, the risk of cavitation reduces [8,9,10]

Methods

Results

Conclusion