Study On Hydraulic Characteristics Of Energy Dissipation Combined With Step And New Type Integrated Stilling Basin

As a major water conservancy country,China has long been recognized as a major strategy for governing the country and maintaining stability in water conservancy construction.Flood discharge and energy dissipation are usually a major and complex issue in water conservancy construction.After comprehensive consideration and overall planning of the composition and layout of buildings,relying on reservoir engineering,hydrogeological and hydrological and meteorological conditions,a safe and economical energy dissipation is reasonably selected.So that the discharge structure can fully dissipate energy during operation and ensure the safety of downstream rivers.Although stepped spillway has obvious advantages in construction and energy dissipation compared with smooth spillway,high-speed water flow can easily cause cavitation damage on stepped surface under the condition of high-water head and large single-width flow.As one of the classic energy dissipation methods,underflow energy dissipation has strong applicability under different geological conditions,but it often increases the engineering volume and cost of the project due to the need to build large-scale energy dissipation pools.In order to solve the shortcomings of the two energy dissipation methods when operating separately,underflow energy dissipation and step energy dissipation are combined,which can not only reduce the degree of cavitation and cavitation on the step surface under high-speed water flow,but also reduce the energy dissipation required for underflow energy dissipation,which has certain guiding significance for the design and selection of energy dissipators.Combining three methods of hydraulic model test,numerical simulation and theoretical analysis,the energy dissipation effects of steps and different types of stilling pools are discussed.At the same time,by analyzing and researching the hydraulic characteristics of the combined energy dissipation of the stepped spillway and the integrated stilling basin of a water conservancy project,the feasibility of the combined energy dissipation of the steps and the new integrated stilling basin is determined.The main results of this paper are as follows:(1)Several traditional flood discharge and energy dissipation methods are introduced,and the domestic and foreign research progress of stepped energy dissipation and related theories of model tests and numerical simulations are studied and summarized in detail.(2)Combined with a water conservancy project,a hydraulic model test and numerical simulation study of the combined energy dissipation of a stepped spillway and a conventional stilling basin were carried out.The results obtained by the two methods are basically the same.On the one hand,the reliability of the results obtained by the two methods are mutually verified;on the other hand,the accuracy of the numerical simulation parameter setting is also proved.Through the research and analysis of the hydraulic characteristics of conventional stilling basins such as flow pattern,water depth,pressure,velocity,etc.,the results show that the conventional stilling basins are not sufficient for flood discharge and energy dissipation and fail to achieve the purpose of energy dissipation.(3)Based on the results of model tests and numerical simulations,nine optimization schemes for stilling pools were proposed,including adding through sills in the stilling pool,adding different types of tail piers,and widening and deepening the stilling pool.And using FLOW-3D software to carry out numerical simulation research on nine kinds of joint energy dissipation schemes,comprehensively compare the hydraulic characteristics and energy dissipation effects of each optimization scheme,and determine the optimization scheme of the step and the new integrated energy dissipation pool.(4)The comparison between the model test and the numerical simulation results shows that under the same conditions,the step and the new integrated stilling pool combined energy dissipation method proposed in this paper are more smooth and smoother than other energy dissipation methods.The water jump phenomenon is obviously eliminated,the velocity distribution along the way is more uniform,the flow rate out of the pool is smaller,the energy dissipation effect is better,and the energy dissipation rate is higher.This paper verifies the reliability of the two methods of model test and numerical simulation in solving the energy dissipation problem of actual engineering.Numerical simulation can provide program screening for project optimization,saving the time and cost required for model testing;The model test can carry out corresponding research on the optimal scheme of numerical simulation,and observe the actual flow and flow pattern of the water flow to further determine the feasibility of the scheme.The research results of this paper can provide reference and basis for practical problems of similar projects.