Experimental Research on the Presented Water-Surface Curve of Skimming Flow on Stepped Spillways and Energy Disspation
Zhang Zhichang(1),Zeng Dongyang(2),Liu Yafei(1)
(1 Xi'an University of Technology Xi'an 710048) (2 South west JiaoTong University)

Abstract: The flow pattern the water-surface curve and the effect of energy dis sipation are investigated via hydraulic model test. There are two flow patterns on the stepped spillway——internal vortex and main stream zoom on the fictitious bottom. The distribution of water-surface curve is related to the discharge, the size of steps and the density of the entrainment air. when the flow enters the steps, the water surface, due to loss of weight, falls to some extent and rises gradually to a certain height and then lowers slightly. The water surface falls before the flow point of air entrainment and then rises afterwards. When the water flow is saturated in air entrainment, the water depth doesn't change to manifest as a uniform flow in open channel. The energy dissipation of water flow is produced by the accumulation of all steps. The effect of the energy dissipation is greatly enhanced owing to the collision of the water with the steps, the water vortex on the steps and turbulent shearing of water. The energy dissipation rate is 40 to 70% higher than that of the skimming spillway. The calculation methods of the water -surface curve and the energy dissipation rate are proposed.
Keywords: stepped spillways, skimming flow, flow pattern, water-surface curve, energy dissipation.