Effects of Step and Cavity Shapes on Aeration and Energy Dissipation Performances of Stepped Chutes

Abstract

The effects of step edge and cavity shapes on skimming flow properties were investigated in a large-size 45° stepped chute model configured with uniform triangular steps, partially blocked cavities, and chamfers. The focus of this experimental study was the air–water flow regime and the energy dissipation performances. Visually, the partial cavity blockage and chamfers were respectively associated with an increase and a decrease in flow stability, while causing no substantial change in the general flow regimes. Comparisons of characteristic air–water properties indicated better aeration performance for the sharp edges than for the chamfers. A substantial reduction in friction factor was observed with the chamfers, while partial cavity blockages appeared to slightly improve flow resistance. A strongly negative correlation between total air entrainment and flow resistance was identified, which was more observable for the sharp edges. A comparative study revealed that sparsely spaced sharp edges at slopes between 3 and 45° might be optimal in terms of aeration and energy dissipation performances.