| Cross free-pressure tunnel is widely used in the construction of water conservancy project in China.However,there are many relevant problems at the intersection of the water diversion and conveyance projects,such as the flow pattern is disordered,the turbulence is mixed violently,the flow velocity is too fast,and the mixed free-surface-pressure flow etc.,which cause hidden dangers to the safe operation of the project.In order to ensure the safe operation of the hydro-junction,it is necessary to study and analyze the relevant hydraulic characteristics of the water flow of the intersection of the cross free-pressure tunnel.Therefore,it is of great significance to analyze the influence of the hydraulic characteristics of the water flow at the intersection on the cross free-pressure tunnel in order to ensure the safe and stable operation of hydro-junction in the water conservancy project.In this paper,ANSYS ICEM is used to conduct 3d modeling and mesh division of the cross free-pressure tunnel,ANSYS FLUENT is used for simulation calculation.The discrete method is the finite volume method,the turbulence model is Realizable k-? model,the solution method is PISO algorithm(second-order upwind discrete),and the solution method of gas-liquid two flow is VOF method.Finally,Tecplot is used to post-process the calculation results.The main contents of this paper are as follows:(1)the research results of cross flow by scholars and experts at home and abroad in the past were summarized,and the basic theoretical knowledge of the flow at the junction of open channels in natural rivers was introduced.(2)the theoretical basis of numerical simulation was expounded,and the mathematical model,calculation method,control equation and other basic theoretical knowledge of numerical simulation were introduced.(3)the model of the cross free-pressure tunnel was constructed and calibrated.ICEM software was adopted to establish a generalized model of the cross free-pressure tunnel with the intersection angle of 52 degrees and divide the grid.The initial and boundary conditions of the model were given.the finite element calculation software FLUENT was used to carry out simulation calculation on the cross free-pressure tunnel model under different flow conditions,and the simulation results obtained after the calculation were compared with the experimental data to verify the correctness and rationality of the method of the numerical simulation calculation.(4)hydraulic characteristics of the water flow such as flow velocity,pressure,water depth,and pressure head of floor etc.at sections of the intersection of the cross free-pressure tunnel under different confluence ratios,different intersection angles and different water depth were studied and analyzed,and relevant conclusions were drawn. |
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