Three-Dimensional Numerical Simulation Of Flow Conditions In The Upper Approach Channel And Mouth Gate Area Of A Narrow And Deep River Hub

Due to the growing demand for inland navigation and the increasing safety of ships,it has become particularly important to study the water flow conditions in narrow river channels in mountainous areas.The water flow conditions are critical to the safe movement of ships,not only determining the safety of ships entering and leaving the locks,but also a key factor in determining the navigability of the hub.In this paper,based on the overall experimental study of the Shanxiu lock hub,a systematic study was conducted on the setting of a submerged dam in the upper approach channel mouth gate area and the local opening of the bulkhead wall to improve the water flow conditions,and a two-and three-dimensional mathematical model was established to clarify the impact of the angle of the submerged dam on the water flow conditions in the upper approach channel:(1)Using MIKE21 software to carry out two-dimensional numerical simulations of the recommended scheme and the recommended scheme without a submerged dam scheme for the water flow conditions in the upper approach channel gate area of the second-line locks,the results will be compared and analysed to determine the feasibility of setting a submerged dam in the upper approach channel gate area of the hub,and the results of the two-dimensional numerical simulations will be used as boundary conditions for the three-dimensional numerical simulations to ensure the accuracy of the three-dimensional numerical simulations,for the study of the Shanxiu hub upper approach channel gate The results of the 2D numerical simulation were used as the boundary conditions for the 3D numerical simulation to ensure the accuracy of the 3D numerical simulation,and to pave the way for the study of the navigable water flow conditions of different types of submerged dams at the approach gate of Shanxiu Hub.(2)The FLOW 3D software was used to carry out 3D numerical simulations for the recommended scheme of the Shanxiu expansion project without submerged dams and with submerged dams at angles of 30°,45° and 60°.The larger the angle of the submerged dam,the smaller the angle between it and the flow direction,the smaller the role of the submerged dam in regulating the flow.Therefore,it is recommended that a smaller angle of diversion be installed in the upper approach channel to improve the flow conditions in the gateway area.(3)Using the recommended scheme of the overall physical model of the built Shanxiu lock expansion project,tests were carried out on the partial opening of the upper approach channel bulkhead,exploring the effects of three options: opening the hole near the upstream head of the approach channel,not opening the hole in the upper approach channel bulkhead and opening the hole at the bottom of the middle and lower sections of the approach channel on the navigable flow conditions in the approach channel.The three-dimensional numerical simulation was carried out using FLOW 3D software to compare and analyse the three options and determine the optimal solution.Under the recommended layout scheme proposed by the Shanxiu lock broad energy engineering physics model,the open hole scheme near the upstream head of the upper approach channel leads to a larger return flow range and intensity in the upper approach channel and the mouth gate area,while the water flow conditions in the middle and lower sections of the approach channel are not much different from,or even slightly better than,the open hole scheme in the middle and lower sections.Therefore,it is recommended to use the recommended solution(opening holes at the bottom of the lower and middle sections of the approach channel)as the design solution.(4)The Shanxiu lock expansion project is the first of its kind to set up a submerged dam at the upstream approach channel gate to improve the navigable water flow conditions,so it is necessary to explain the rationality of this improvement measure from a theoretical point of view;the analysis of the partial opening of the upper approach channel bulkhead is carried out to explain the impact of the three design options on the navigable water flow conditions from a three-dimensional perspective,which can provide reference value for similar projects.