| In recent years,the construction of water conservancy project has become a priority in our energy development strategy.However,the layout of drainage buildings is often affected and restricted by terrain and other conditions,and the internal flow patterns of drainage buildings are also complicated.At the same time,the relevant issues associated with the shape optimization and discharge capacity of the spillway tunnel are becoming increasingly significant.The effect of this,for example,higher requirements are proposed here to justify the operation.The spillway tunnel is an important drainage building in the project of water conservancy.It is always built in the deep mountain canyon area with the complex geological conditions.This severe environment brought about a narrow excavation site and the conundrums in construction,and this kind of engineering has high requirement for construction quality.The spillway tunnel undertaking the important task of flood discharge.Therefore,the reasonable design of the spillway is the main factor of engineering safety.It has closely related to the overall safety and economy of water conservancy projects.In the context of practical hydraulic engineering,this study investigates the hydraulic characteristics within the spillway tunnel,based on numerical simulation tests and physical modeling experiments.The main content and research results are as follows.(1)The hydraulic model is made by using the gravity similarity criterion,and the model scale is 1:35.With this method,several bodily form schemes of the transition section has been simulated and investigated.In this paper,hydraulic factors such as flow velocity,hydro-dynamic pressure and water-surface curve of the spillway tunnel are calculated.Meanwhile,the distributing characteristics of flow state,velocity field and pressure field were refined simulated and analyzed.Considering about the inferior impact resistance of the downstream channels and banks,meanwhile,analyze the position and shape of the scour hole.(2)In order to improve the flow regime of the transition section of the spillway,this experiment optimized the straight wall located in the inlet of the spillway tunnel to broadening formation and,rounded off the section that is faces the upstream.,the inlet side wall of the spillway tunnel is optimized by the slope type right side wall to the horn inlet,and the flow area is repaired to guide the water flow smoothly.In this paper,the most economical and rational optimization scheme is given,through the optimal design and comparative analysis of the transition section.Ultimately,several unfavorable phenomena,such as the turbulent flow of the spillway tunnel and the water-wings near the side walls,could be effectively improved via this method.The result shows that this kind of design method can satisfy the requirement of engineering with better project benefit.(3)The water head of this spillway tunnel is large.When the spillway tunnel is working,the flow velocity is higher along the path.When it is working,the velocity is high along the path,and the cavitation problem is worthy of attention,so that the cavitation erosion problem is worthy of attention.According to the model test results,this study analyzed the local flow regime and velocity of the spillway tunnel.According to the design specification requirements,this study set two air entraining facilities in the position,where the flow rate is higher,near the circular section of the spillway tunnel.Then,this study analyzed the flow regime,velocity and the pressure of near the two air entraining facilities.Compared with the preset,the rationality of the aeration position was verified,and the possibility of cavitation damage was reduced.(4)Numerical simulation technique,serving as an important method to study the turbulent motion in complex regions.It is widely accepted by many advantages,such as accuracy,economy,time consuming,avoiding the scale effect and so on.The three-dimensional flow field has been simulated numerically with the aid of RNG k~ epsilon turbulence model in case of unsteady flow and the VOF method interface tracking technology.The coupling of pressure and velocity field is calculated by PISO algorithm.With this method,several bodily form schemes of the transition section and the air entraining facilities has been simulated and investigated.These methods avoided the scale effect and,as a result,the distribution of flow,velocity field and pressure field in two typical working conditions are analyzed,including the flow velocity,dynamic water pressure and surface line.This study analyzed the regularities of distribution of the hydraulic elements systematically.(5)The numerical results are used to verify the accuracy of the data obtained from the hydraulic model test.The results are well-fitted.The research results show that the reasonable design of spillway body shape is the key to the safe operation of the reservoir.Optimizing the inlet type of the spillway can effectively improve the flow state in the control section of the sluice chamber.It has an important influence on the distribution of the overall flow pattern and velocity of the spillway.The rational design of the length of the tapered section is the key to optimization and safe operation of the spillway.This paper studies the hydraulic characteristics of the spillway tunnel and finally proposes a feasible and optimal design scheme.Research achievement provides technical support for complex flow field.The optimization ideas proposed in this paper have been applied to this project. |
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