| In order to solve the problem that there is a large range of oblique flow and other bad flow state in the upstream entrance area in the design scheme,it can’t meet the safe navigation of ships,and to reduce the influence of bend flow,terrain and boundary conditions at the bifurcation on the flow conditions in the entrance area.Based on the reconstruction project of Qingshan pivot in Lishui,this paper adopts the method of numerical model,whole fixed bed physical model and ship model test,the flow characteristics of navigational flow in upstream entrance area of bending bifurcation river section,improvement measures for flow conditions in upstream entrance area and discharge capacity under improvement scheme were studied,and obtains the following results:(1).The influence of structural parameters of diversion pier on flow conditions:1)when the length l and relative spacing d/l are determined,the cross flow decreases gradually with the increase of the number;2)When the number N and length l are determined,the cross flow velocity at the last diversion pier decreases first and then increases with the increase of relative spacing,and the effect is the best when the relative spacing is 1.0;3)For the same number of diversion piers,when the relative spacing of diversion piers is determined,the effect is the best when the length of diversion pier is 20m,which is about 1/20 of the net discharge width of the hydro project;4)The relative spacing,number and length of diversion piers are the same.When the diversion piers are arranged in parallel along the navigation wall,the flow conditions are the best.(2).As for the improvement scheme,the flow conditions in the entrance area have been improved to some extent compared with the design scheme,but still can’t meet the requirements;Under the second plan,the water flow condition has been further improved,but it can’t meet the requirement of moderate economy;Scheme 3 improves the flow conditions in the entrance area by reducing the number of diversion piers,dredging to 43.0m in the upper 2000m range of the right braided dam and stopping in a single row at the left braided berth.In order to improve the navigation of the upstream entrance area of Qingshan pivot,it is found that only by combining various improvement measures can the flow conditions be effectively improved so that the ship can navigate safely and provide reference for similar projects. |
