| With the rapid development of the national economy,large-scale hydropower development has become one of the important ways to solve my country's energy problems.Horizontal swirling energy dissipation is an eco-environmentally friendly energy dissipation technology,which can effectively solve the problem of high-speed water flow caused by high dam construction.However,the cavity swirling flow pattern in the horizontal swirling spillway tunnel is complicated,and the experimental measurement technology has certain limitations,and it is impossible to measure its internal flow field parameters.In this paper,a typical horizontal swirling flood discharge tunnel is used as the research object,and the method of combining model test,numerical simulation and theoretical analysis is used to conduct an in-depth analysis of the internal flow field characteristics of the cavity swirl,and then to study the motion characteristics of the combined vortex in cavity swirl.The main results are as follows:(1)On the basis of the model test,the numerical simulation method is used to explore the optimal mathematical model suitable for simulating the inner cavity swirl of the horizontal swirl energy dissipater.Among them,the grid,turbulence model,boundary conditions and algorithms have a great influence on the accuracy of the numerical simulation results.The results show that the Realizable turbulence model,the Sharp processing method of the VOF method,the PISO algorithm,the PRESTO discrete model and the QUICK discrete format can be Realize the accurate simulation of the internal flow field characteristics of the cavity swirl.(2)Using the existing optimal mathematical model as the basis of calculation,numerical calculations are carried out on the working conditions of the weir h=0.95 D,1.43 D,1.56 D,1.90 D,2.33 D and so on.As the discharge flow increases,the water flow in the inlet section shows the flow pattern evolution process of free flow,transition flow and submerged flow successively;the rotating water flow forms a nearly circular cavity in the horizontal hole,and the diameter of the cavity changes first and then increases along the way At the same time,the radial pressure and tangential velocity of the cavity swirl are in accordance with the Rankine combined vortex distribution;the swirl angle,turbulent kinetic energy and turbulent dissipation rate all show a decreasing trend along the way;the horizontal swirling internal energy dissipation The tool has a higher energy dissipation rate,and its cumulative energy dissipation rate is 66.12%;the energy dissipation effect per unit length of the cavity swirl between X=0 to X=5D section is better than X=5D section to X=30D section.The reason is that the thickness of the rotating water layer between the X=0 to X=5D section is rapidly reduced,the flow velocity gradient is large,the shear turbulence between adjacent flow layers is intense,and the degree of energy dissipation is much greater than that after the X=5D section.Stream section.(3)Based on the radial pressure and tangential velocity of the cavity swirling flow satisfying the distribution law of the Rankine combined vortex,the radial distribution of the cavity swirling combined vortex index is analyzed,and the inner side of the swirling water flow area is the quasi-forced vortex motion,the outside is quasi-free vortex motion.The theoretical formula of the radial pressure difference in the swirling area is deduced,and the theoretical value and the simulated value of the radial pressure difference are compared and analyzed.The two are in good agreement,which proves that the rotating water flow characteristics in the horizontal tunnel conform to the combined vortex motion law.Finally,the difference between the cavity swirl combined vortex and the Rankine combined vortex is explained from the aspects of the fluid force status,composition structure,generation mechanism and energy loss,and the motion characteristics of the combined vortexes of the cavity-swirling are revealed. |
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