| Entering the new era,the development of Chinese water conservancy is in the ascendency.With the completion of water conservancy projects in the eastern part of China,people gradually shift their attention to the western region with rugged cliffs and ravines.In hydraulic engineering,spillway tunnel is a very important drainage structure,which plays an important role in discharging flood to the downstream and ensuring the safety of the junction.Therefore,the safety,economy and efficiency of spillway tunnel design are not only related to the determination of various technical indicators of hydraulic engineering,but also directly related to the safe operation and cost control of the project.However,in actual engineering construction,the flow pattern of the overflow tunnel varies with the boundary conditions.Therefore,it’s vital to investigate the optimization of discharge capacity and overflow tunnel’s shape for the sake of improving the flood discharge capacity and protecting the spillway tunnel body effectively.Taking the spillway tunnel of a hydraulic engineering in Xinjiang as the research background,the hydraulic characteristics of the overflow tunnel with different design schemes under different water level conditions are studied and optimized by using the method of model test and numerical calculation.The main research contents and achievements of this paper are as follows:(1)A 1:50 scale hydraulic model was made by using Froude number similarity criterion,and experimental studies were carried out under conditions of different characteristic water levels to observe the flow pattern of the spillway tunnel,measure the water depth and velocity of each section along the spillway tunnel,collect the pressure of each measuring point along the spillway tunnel,and analyze the hydraulic phenomenon.(2)In order to improve the flow state of the gradient section and the downstream of the aeration culvert in the spillway tunnel,the gradient section and the aeration section are optimized.Appropriately extend the length of gradual change section,adjust the type and size of aeration bump.After optimization,the turbulent flow pattern of the downstream water flow is effectively improved,the water wing of the downstream side wall of the inclined shaft section is greatly reduced,and the water flow can enter the spillway tunnel body smoothly.(3)In view of the problem that the erosion reduction effect of the aeration is not ideal after the height of the aeration culvert is reduced,a wedge aeration trough is added,and the rationality of the aeration facility is verified by studying the flow pattern,water depth,pressure,flow rate,wind speed and flow rate of ventilation well,and cavitation number of the water inside the aeration facility.The optimized aeration facilities Can improve the adverse phenomena effectively such as insufficient aeration in the spillway tunnel and serious water accumulation in the aeration tank,and the occurrence probability of cavitation is greatly reduced.(4)The RNG k-ε turbulence model in commercial software Ansys Fluent was used to simulate the complex turbulence movement in the spillway tunnel prototype.The hydraulic characteristics of the original scheme and the optimized scheme were obtained in four typical working conditions,and the overall flow pattern,water depth,flow velocity and pressure distribution along the spillway tunnel were analyzed.The rationality and practicability of the numerical calculation method and the turbulence model were verified by comparing the results of model test and numerical calculation.The results showed that the hydraulic elements of the two models were basically the same,and the numerical calculation can be effectively applied to the simulation of the spillway tunnel.To provide design ideas,theoretical basis and reference experience for practical hydraulic engineering,this paper conducts a comprehensive study on the hydraulic characteristics of the spillway tunnel and verifies the scientific and rational nature of the numerical model used. |
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