| Water shortage will cause serious ecological and environmental problems,to a certain extent limit social development,the construction of cross-basin water transfer projects because it can solve the problem of excessive differences in water content in different regions.In actual engineering,unsteady flow regulation and operation is the norm,but frequent scheduling operations are often accompanied by drastic changes in flow patterns,and the project itself has huge safety risks.Therefore,it is of great significance to study the sensitivity of hydraulic response in the unsteady flow regulation process and summarize the change law of hydraulic characteristics of different control modes,which is of great significance to reduce the safety risk in the actual project operation.In this paper,taking the Huangchigou water distribution hub as the research object,based on the RNG k-ε turbulence model,combined with the free liquid level tracking method,the non-constant flow process of emergency regulation and control of the downstream of the water distribution hub was numerically simulated and studied.The main contents and achievements are as follows:(1)Perform mesh-independent analysis and select the appropriate turbulence model.The hydraulic characteristics of the water transmission condition simulated by different grid sizes and turbulence models were compared,and the grid size and turbulence model with high calculation accuracy of the flow characteristics and consistent flow patterns of the dividing tank were selected with the test results.In order to verify the applicability of the 3D model,the water transmission conditions of the two water distribution hubs were simulated and calculated,and the relevant hydraulic characteristic parameters obtained were consistent with the test results.(2)Numerical simulation study on the unsteady flow process of accident operation regulation of the North Main Line of the water distribution hub.The hydraulic response characteristics of the two water transmission schemes of 35m3/s and 20m3/s in Qinling Tunnel under ten different gate regulation modes were analyzed,and the influence of different control methods on the flow pattern of the water distribution pool and the hydraulic characteristics near the gate was studied.After the closure of the North Main Line gates,there was a small increase in the flow of the South Main Line tunnel of the two water transmission schemes,and the side trough spillway played a diversion role.The elevation of the water surface in the dividing pond fluctuated and increased,and the amplitude of the upper left corner of the dividing pool was relatively large.Two backflow vortices formed in the pool,further causing lateral water inflow at the entrance of the South Main Line tunnel.At the moment when the gate of the North Trunk Line begins to close and is completely closed,the pressure in front of the gate fluctuates sharply,and the pressure head changes by 1.65m when the flow rate of the Qinling tunnel is 35m3/s and the water transmission scheme is closed for 25s.(3)The unsteady flow process of accident operation regulation of the south trunk line of the water distribution hub was numerically simulated and calculated,and the hydraulic response characteristics of the three water transmission schemes of Qinling tunnel flow of 50m3/s,35m3/s and 20m3/s under the closing speed of 12 different gates were studied.After the South Main Line gate began to close,the water surface of the inlet of the South Main Line tunnel fluctuated sharply,and the water surface undulation in the right return area of the main stream and the center of the dividing pond was relatively small.The flow velocity on the left side of the inlet section of the South Trunk Line tunnel is greater than the flow velocity on the right,and the flow velocity on the left side of the inlet section of the North Trunk Tunnel is greater than the right side,and then the water flow gradually penetrates into the North Main Line according to inertia,the flow velocity on the left side of the section gradually decreases,and the flow velocity on the right side begins to increase.When the South Main Line gate begins to close,too fast a closing speed will cause a sharp fluctuation in the pressure in front of the gate. |
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