Numerical Simulation Of Flow In The Spirogyrate Stepped And Imbricate-floor Spillway

Stepped dissipater is a method to dissipate water energy by steps set on the spillway, and it has characteristics of high dissipate efficiency, which is taken seriously by engineering field because it can reduce scouring behind the rear apron and simplify the anti-scour facility so that it can save investment. The stepped dissipater become a rapidly improved way of energy dissipation especially the continuous right-angle steps which is commonly applied in spillway of gravity dam with steep gradient. Recent years, a kind of discontinuous spirogyrate stepped spillway catch the attention of engineer for its simple structure, easy construction and obvious effect on energy dissipation. Its difference from the traditional kind in structural is that it will set a step-down on the spillway base plate at a distance. This new kind has already applied in some gradual slope spillways. However, the research on hydraulic characteristics of this new kind is not thorough.The results of numerical simulation of imbricate-floor shows that the aerator have a considerable disturbance to water depth in the chute so that the water depth was considerably increased, the water depth behind bucket and the cavity length will increase with the height of bucket increasing, the negative pressure of step's root will increase with the height and angle of the bucket increasing meanwhile the pressure distribution on the base plate will be more nonuniform. For this article simulated two bottom slope, The step height in 0.6 m scope, With the step height increase, and the range of energy dissipation ratio the increased obviously, But the step height more than 0.6 m, The growth of energy dissipation ratio is smaller. When the bottom slope must, spirogyrate stepped spillway energy dissipation ratio increase with decreases of steps span, but, when the steps spacing reduced to certain value, The growth of energy dissipation ratio begin to slow down, This kind of phenomenon show that steps spacing with bottom slope relevant. And the orthogonal continuous continuous steps contrast results indicate at the height of steps smaller 0.5 m, spirogyrate stepped spillway energy dissipation ratio slightly less than orthogonal continuous steps, And in the steps height larger cases, The spirogyrate stepped spillway and the orthogonal continuous steps have similar energy dissipation ratio.According to the numerical computation of pressure, the results show that, the maximum negative pressure of the step's root increases when the step height decrease and the distance increase. When step height is more than 0.4m and distance is less than 5m, the cavitation phenomenon won't occur.The results of numerical simulation of imbricate-floor shows that the aerator have a considerable disturbance to water depth in the chute so that the water depth was considerably increased, the water depth behind bucket and the cavity length will increase with the height of bucket increasing, the negative pressure of step's root will increase with the height and angle of the bucket increasing meanwhile the pressure distribution on the base plate will be more nonuniform.