Abstract
The original design scheme of ladder-shaped spillways in certain reservoirs is improved by using a hydraulic similar model experiment. The results of the original scheme demonstrate that the stilling basin cannot meet the requirement of safe discharge, and the flow state at the end of the stilling basin is violent and chaotic. The experimental method of the physical model was used to optimize the design of the spillway without changing the original plane layout. First, three steps in the ladder are added. The stilling basin is then replaced by the torsion plane. Finally, the longitudinal slope of the tail channel section is altered, and an experimental investigation on the flow state and energy dissipation rate is performed. The conclusions are drawn that the flow state of the water is obviously improved, and the energy dissipation rate increases; the optimal scheme produces the expected effects.
Highlights
The water movement in a ladder-shaped spillway can represent three types of flow states according to the unit width flow and the height and slope of the ladder, i.e., drop flow, slip flow, and transitional flow [9, 10]. e occurrence of slip flow is regarded as the design criterion of ladder-shaped spillways
Essery [16] performed the experimental investigation on the hydraulic characteristics of ladder-shaped spillway during the 1970s, and the water flow is classified into Nappe flow and Skimming flow according to Essery’s suggestion; the model similar experiment of ladder-shaped spillway is performed by Christodoulou [17] in 1993, and the results demonstrate that energy dissipating rate is related to the Geofluids clinical depth of water and the height and number of ladders; the time-averaged pressure distribution law of ladder-shaped spillway under the conditions of different heights and gradients of ladder is investigated by Cui [18] in 2012 by using the hydraulic model experiment
To improve the flow state of water in the spillway, a series of experimental investigations focused on the optimal structural form of the spillway have been performed, and conclusions are drawn as follows: (1) Based on the improved design scheme, aerification of the drainage of water at the stepped energy dissipation section of the discharge chute is sufficient under the various different cases
Summary
To eliminate the residual energy of the water head crossing the dam or weir in a hydropower project [1], slip spillways or overflow dams are often applied to flip buckets for energy dissipation, and the stilling basins are constructed for the energy dissipation of the bottom flow [2]. Ey are characterized by good energy dissipation efficiency, low cost, and a small level of effort in construction [5, 6]. For these reasons, the ladder-shaped spillways have been investigated by many researchers [7]. A great number of experimental investigations on the energy dissipation characteristics of slip flow of the ladder-shaped spillways have been performed [14], but due to the complexity of water movement, unanimous conclusions have not been obtained [10, 15]. The optimization of water flow can shorten the time of construction and can reduce the length of sting basin, so the optimization of flow state in the ladder-shaped spillway has great significance for the engineering design
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