Research On The Layout Of The Approach Channel Under The Rongjiang Da BU Second Line Locks And The Navigable Water Flow Conditions In The Mouth Gate Area

Rongjiang River belongs to the West River system of the Pearl River basin,is the middle section of the Liuzhou River,a first-class tributary of the West River,for the north route of southwest water transport to the sea channel.Tai Po Water Conservancy Hub is located in the Rongjiang River section of Liuzhou River Basin.The low grade and small scale of the already built locks make it difficult to adapt to the requirements of large transport vessels,which also becomes a bottleneck for the overall effectiveness of the Rongjiang River channel in Liuzhou Basin,the northern route of southwest water transport to the sea.Therefore,in order to improve the level of the Rongjiang channel,it is necessary to expand the capacity of the Tai Po Junction Locks.In this paper,based on the project of Tai Po water conservancy hub,the research idea of combining physical solid model and numerical simulation is adopted to study the navigable water flow conditions of the construction design scheme,optimization scheme 1 and optimization scheme 2 of Tai Po water conservancy hub project,and provide corresponding technical support to solve the navigable problems of the approach channel of the locks,and take corresponding engineering measures to solve the navigable problems of the approach channel.The main contents include.(1)On the basis of the full study of domestic and foreign locks navigation related information,the lower approach channel layout,the standard of hub navigable water flow conditions,the existing built locks lower approach channel mouth gate area navigable water flow conditions research status,the development of research methods and trends,etc.are summarized and explained.(2)Through the experimental study of the hydraulic model of Tai Po hub,it is found that the design scheme will form unfavorable flow patterns of plunge and slope flow in the approach channel gate area,and form bubbling water and extensive backflow in the mooring section of the approach channel,and affect the hub discharge and flooding of the river downstream of the dam.Therefore,two layout options were proposed: Optimization Option 1 and Optimization Option 2.By summarizing the test results and considering various influencing factors,it was concluded that the optimized option 2 could better meet the test requirements and effectively improve the flow pattern in the lower approach channel,the mouth gate area and the connecting section,and the lateral flow velocity value and exceedance range were reduced.It effectively reduces the influence of the lower approach channel arrangement of the locks on the hub discharge and river flooding.(3)Starting from the numerical calculation method of two-dimensional water flow,the calculation principle of MIKE21 software is explained,including the establishment of control equations and numerical solution method.Then,the model is selected,the river network file is created,the grid is divided,the key parameters of the model are determined,and the numerical simulation solution process is explained.Finally,the mathematical model was verified: the mathematical model can correctly simulate the flow state in the gate area of the approach channel under different working conditions,and the numerical calculation is practical and feasible,and can meet the actual requirements well.(4)Through the numerical simulation study of the optimized scheme navigational conditions,three aspects are analyzed and studied: construction of the model,numerical simulation results,and analysis of calculation results.The numerical simulation results are analyzed and compared by water level,total water depth,vector distribution,etc.From the results,it can be seen that the physical model and numerical simulation are compared with each other,and it can be confirmed that the arrangement plan of the optimized scheme II is feasible.(5)As the two-dimensional model cannot accurately present the water flow of the bulkhead structure.Therefore,the three-dimensional water flow mathematical model is used to conduct a preliminary study on the layout type of the bulkhead structure of the optimized scheme,to examine the navigable water flow conditions in the lower approach channel mouth gate area,and to analyze and compare the total water depth map,the horizontal surface mouth gate area velocity vector map,and the lateral flow velocity distribution map in the mouth gate area for the three-dimensional numerical simulation results.To ensure the rationality of the diversion channel bulkhead arrangement.And the recommended scheme of the downstream approach channel layout is proposed.