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Hydraulic design of stepped spillway using CFD supported by physical modelling: Muskrat Falls hydroelectric generating facility
Published in Jean-Pierre Tournier, Tony Bennett, Johanne Bibeau, Sustainable and Safe Dams Around the World, 2019
J. Patarroyo, D. Damov, D. Shepherd, G. Snyder, M. Tremblay, M. Villeneuve
In general, the flow over a stepped spillway can be characterized by stable vortices that develop at each step, filling the area between the main flow and the step surface. Water flows over the stepped spillway as a stream skimming the steps and cushioned by re-circulating fluid trapped between them (Chanson, 1993). Vapour bubbles or cavities can form when water is subjected to localized pressure reductions below the vapour pressure of water. As the vapour cavities travel with the flow and local pressure conditions rise, these cavities implode and result in a phenomenon known as cavitation. Repeated implosions near a surface boundary, such as the steps of the spillway surface, can erode the surface material. Cavitation on chutes is initiated for high velocity flows and local pressures below the vapour pressure (Falvey, 1990). The risk of cavitation is determined using the cavitation index as defined by Equation 1 below:
Stepped Spillways
Published in R. M. Khatsuria, Hydraulics of Spillways and Energy Dissipators, 2004
A stepped spillway can be designed so that each step corresponds to an independent stilling basin with hydraulic jump, formed with the provision of an overflow weir at the end of each step, as shown in Figure 5. Aigner (2001) has suggested a procedure for the design of such a spillway. For a given unit discharge (and hence yc) and step height h, the conjugate depth y2 of hydraulic jump is calculated on the basis of the total energy entering the step: E0=h+w+y0+yc32(w+y0)2
Roller compacted concrete and stepped spillways: From new dams to dam rehabilitation
Published in J.A. Llanos, J. Yagüe, F. Sáenz de Ormijana, M. Cabrera, J. Penas, Dam Maintenance and Rehabilitation, 2017
Table 1 list several RCC dams incorporating a stepped spillway on the downstream face. Many of the dams have incorporated a stepped spillway with the benefit of hydraulic model investigations, such as Upper Stillwater, Monksville and Stagecoach in the USA, De Mist Kraal, Wolwedans and Zaaihoek in South Africa and La Puebla de Cazalla, Sierra Brava and Boquerón in Spain, Shuidong in China, and Nakasujigawa in Japan, among others. An extensive list of model and prototype studies conducted in the last three decades can be found in Chanson (2002).
Numerical investigation of air–water flow properties over steep flat and pooled stepped spillways
Published in Journal of Hydraulic Research, 2018
Shuai Li, Jianmin Zhang, Weilin Xu
Spillways are commonly used as floodwater release facilities in reservoir dams (Chanson, 1995; Hansen & Reinhardt, 1991). Stepped spillways are important for dissipating hydraulic energy because of their stepped geometries. When flow passes a stepped spillway, the steps, which have a high surface roughness, increase the air entrainment and energy dissipation and allow the size of the downstream energy dissipater to be reduced (Chanson, 2001). Skimming flow is dominant because most prototype stepped spillways operate under large discharges. The flow is characterized by high aeration, significant energy losses and momentum exchange (Chanson, 2001; Chanson & Toombes, 2002a; Felder & Chanson, 2009; Gonzalez & Chanson, 2007; Ohtsu, Yasuda, & Takahashi, 2004; Rajaratnam, 1990).
Particle swarm optimization-based LS-SVM for hydraulic performance of stepped spillway
Published in ISH Journal of Hydraulic Engineering, 2020
Kiyoumars Roushangar, Samira Akhgar
The data used in this paper is derived from experimental results with physical models as listed in Table 1. The experimental results indicated that the type of flow regime might be considered as a function of the critical flow depth, step height and slope of stepped spillway. Three different flow regimes, namely, the nappe, transition and skimming flow regimes might be occurred over stepped spillway. In the present study, the discharge coefficient and energy dissipation of the stepped spillway is investigated for skimming and nappe flow regimes.