Study On The Shape Of The Left Five-Hole Flood-Discharge And Sand-Sinking Stilling Pool Of Xunyang Hydropower Station

At present,people have achieved more results in energy-saving and anti-shocking,and most of the problems of flood discharge and energy dissipation in high-head and large-single-flow water conservancy hubs have been solved.With the development of society and economy,the hydropower resources with higher water heads are becoming less and less,and the development of low-head gate dam-type power stations has become an important direction for hydropower construction.However,such water-dissipating buildings often have the characteristics of low head,large single-flow,low Froude number,deep tail water and large variation of downstream water level.Therefore,the problems of the dam project in the layout of the hub and the energy dissipation under the gate are particularly prominent.How to properly arrange the hub to meet the flood discharge requirements and choose the appropriate energy dissipator to meet the energy dissipation under the gate is particularly important in the design of the dam.The maximum dam height of Xunyang Hydropower Station is 58m,and the maximum single-width floor discharge of the left five-hole design is 161m~2/s.It is a typical low-head,large single-discharge dam-type water conservancy project.Downstream of the project,the underflow energy dissipation and the deep-type stilling pool are used.In this paper,the left five-hole flood discharge and sand-sinking stilling pool of Xunyang Hydropower Station is taken as an example.The numerical simulation and model test are combined to explore the hydraulic characteristics in the stilling pool of the dam-type water conservancy pivot and choose the appropriate shape of the stilling pool.The main research results are as follows:(1)Through the model test observation of the left five-hole flood discharge and sluice gate of Xunyang Hydropower Station,it is found that:under the original design scheme,the discharge capacity basically meets the design requirements,and the pressure and flow rate are reasonably distributed along the path.However,when the gate is partially opened and the water level difference between the upstream and downstream is large,the exit of the gate hole is likely to form a water jump in the gate chamber,and the water flow is turbulent,which may affect the safe operation of the discharge structure.(2)For the problems of the original design,through the hydraulic model test,the research and analysis of the multiple plunge pools were carried out,and finally the recommended size of the plunge pool was obtained:a 4.5m high straight wall type hurricane is installed at 0+84m below the dam.The recommended results of the model test indicate that:under medium and small flow,the water jump position is moved to the end of the chamber or outside the gate,and the effect of flood discharge and energy dissipation under large flood flow is not affected.(3)In order to further analyze the hydraulic characteristics of the water flow in the stilling pool and obtain continuous flow field information in the pool,The FLOW-3D software was used to simulate the different types of stilling pools,and the hydraulic parameters such as flow regime,flow velocity and energy dissipation rate in different types of stilling pools were obtained.(4)The results of the model test and the numerical simulation are compared and analyzed.It's shown that numerical simulation can better simulate the water jump state of the water flow in the stilling pool.The numerical simulation results are basically consistent with the physical model test results,indicating that the model and method used for this simulation are reasonable.