Air-water flow properties in stepped chutes with modified step and cavity geometries

Skimming air-water flow properties were investigated in a stepped chute configured with triangular steps, chamfered steps, and partially blocked step cavities. The turbulent interactions between air and water were examined using a synchronised system consisting of a dual-tip phase-detection probe and a pressure transducer mounted side-by-side. In comparison to uniform triangular steps, the chamfered steps were found to cause a reduction in air entrainment and an increase in mean velocity gradient next to the pseudo-bottom. Partial cavity blockages appeared to have little effect on air entrainment, but were linked to an increased presence of large-scale structures in the overflow, which likely resulted from a reduction in mutual sheltering between adjacent step elements. The results indicated that modifications of step and cavity geometries might have significant implications on stepped chute design.