Numerical Simulation Study On The Harbor Basin's Backwater Siltation Characteristics Of The Three Gorges Project

Under normal circumstances,after the running in the three gorges reservoir,the section from changshou to luoqi is located in the fluctuation area of backwater.The boundary conditions of this section are complicated,including micro-bending,branching and other forms,and there are often bad water states such as sliding beam water and bubble water,resulting in a large backflow range of this section and serious sediment deposition at the wharf located in this section.herefore,it is necessary to make a study on the varying backwater zone from Changshou to Luoqi.In this paper,a two-dimensional numerical model of water and sediment is used to systematically simulate the movement of water and sediment in the changshou to luoqi reach.The following two cases were compared and analyzed:firstly,the change of water flow movement and the sedimentation change near the wharf before and after joining the wharf;the secondly,after the reef on the upper reaches of the wharf,the movement law of the water flow near the wharf and the mud the change of sedimentation in sand provides a scientific basis and theoretical basis for the sedimentation and control of the river section.The main research results of this paper are as follows:(1)According to the actual measured hydrological data of the river section,it introduces the river's general situation from Changshou to Luoqi,and according to the measured information of Cuntan Station and Qingxichang Station,it analyses the river's water regime and sediment deposition's characteristics.(2)Through the analysis of the current flow conditions of the engineering section and the law of river bed erosion and siltation,it is understood that there is a cumulative sedimentation of sediment at the location of the harbor basin before the port construction.(3)Through the numerical simulation comparison of water flow in two working conditions before and after joining the wharf,it is shown that: after joining the wharf,the upstream water flow velocity decreases slightly,and the remaining changes are not obvious.After joining the wharf,the upstream sediment deposition amount of the wharf is larger than that before joining the wharf,and the downstream sediment amount is smaller than that before joining the wharf.The whole river section of the project shows a trend of cumulative sedimentation.The sedimentation time is mainly from June to September in the flood season.(4)Due to the obstruction of the reef upstream of the wharf,the upstream flow of the wharf is large,and the sedimentation of the harbor is serious.In order to reduce the sedimentation in the harbor,we have adopted the following reef plans for the upstream reef: 2m,fried The reef is 4m,the reef is 6m,and the reef is 8m.The results show that after 8m of reef,the flow velocity of the river is increased,the recirculation range is reduced,and the sedimentation of the harbor is reduced.(5)By comparing the working condition 3 after the reef with the working condition 2,the results show that after the reef is rebuilt,the flow pattern in the upstream of the quay is improved,the flow rate is increased,the siltation in the vicinity of the quay is reduced,and the sediment in the whole engineering section is sedimented.The amount of siltation is also reduced.