Numerical Simulation Of Energy Dissipator With Low-Head Flood Discharging Structure

Low-head water control project is usually composed of sluice gate dam and diversion channel and so on ,which has the characteristics of low-head,large flow,low Fr,deep tail water and low energy dissipation. The analysis results show that: When the Fr<4.5,the energy dissipation is only 20%～45%. A lot of energy is brought to downstream by water ,which result in the downstream channel flow turbulence intensity,great wave and difficulties for energy dissipation. On the other hand, the cost of flood discharging structure generally share the 40%～50% of the whole cost of dam construction, but the cost of energy dissipator take up 40%～50% of the expenses of flood discharging structure. Therefore, the form and reasonable layout become a restrictive important technical problems. Improve the rate of energy dissipation for low Fr hydraulic jump and solve the problem of energy dissipation and erosion , no matter from the technical or economically is very important.In hydropower engineering construction, the research to the characteristics of discharging structure mainly depend on physical model experiment and numerical analysis method. Physical model is a mature methods,the process better approach the water entity,the measured data is the most reliable;Numerical analysis method is fast and strong adaptability, facilitate the design scheme. Two methods have their advantages and disadvantages. So, the combination of physical model and mathematical model become an important method to solve the problem of discharging structure .Take the typical low-head water control project: HengDan hydropower station as the research object. Through the hydraulic integral model test and FLUENT software for HengDan hydropower station's discharge capacity, the flow information in construction,buildings shape optimization and energy dissipation and erosion in hubs downstream are studied and numerical simulated. The numerical simulation is good agreement with the model test data. That shows the model in numerical simulation is reasonable,methods is correct. So it can offer a scientific and convenient way for practical engineering design and research.Using FLUENT software, the numerical simulation area is established by unstructured grids and implicit algorithm, with the standard k—εturbulence model close Reynods equations, using VOF method to track free surface, several kinds of assisted energy dissipator to improve the energy dissipation rate for low-head discharge structure: Wave-shaped bottom dissipator,Diversion Pier with Low Ridge,the USBRⅢtype stilling basin invented by hydraulic laboratory in United States Bureau of Reclamation and T-Shaped Pier+Toe-Shaped Pier are simulated. A variety of flow phenomena in the flow field,Flow structure is predicted. Analysed the rationality of energy dissipation forms and longitudinal compared with the prototype energy dissipator in HengDan Hydropower Station. The results show that: Diversion Pier with Low Ridge dissipator and Wave-shaped bottom dissipator have better effects to the low head,low-Fr hydraulic jump energy dissipation. In practical engineering application, according to engineering specific situation, choose a technically feasible,safe and reliable,good effect for energy dissipation,economic and rational energy measures.