Study On Flow Characteristics Of Downstream Of Baishiyao Complex

Beijiang River is the second largest river in Pearl River system, but the downstreamstandard of navigational channel is only national V. In order to meet the inland watertransportation development, the government plan to improve navigation level to national Ⅲby means of implement the217km waterway regulation project of Beijiang River (Wushi toSanshui Estuary).The study of unsteady flow characteristics between Baishiyao and Feilaixiacomplex and the waterway regulation of19km shoal reach downstream of Baishiyaocomplex are both important parts of waterway regulation project of Beijiang River. In thisthesis, one-dimensional and two-dimensional numerical models had been used to research theinfluence of unsteady flow and waterway regulation project to the downstream navigationalcondition of Baishiyao complex.Firstly, one-dimensional numerical model of75km reach downstream of Baishiyaocomplex has been established to simulate two different daily discharge process of Baishiyaocomplex after verifying the model. In addition, the propagation characteristic of unsteadyflow for this75km reach had been analysed. The result of maximum average flow velocity,maximum water surface slope and maximum water level range indicated that the flowcondition of this reach can meet the kiloton ship’s navigation requirements and satisfy thesafety navigation requirements of water level change per hour. For the second scheme, threedispatching alternatives of Feilaixia complex of without pre-discharge, pre-discharge for12hours and24hours had been calculated. The Feilaixia complex’s reverse regulation effectwith different dispatching modes to the downstream flow characteristics and navigationcondition of Baishiyao complex had also been calculated.Then, two-dimensional flow numerical model of20km reach downstream of Baishiyaocomplex has been established to verify and simulate the flow characteristics with differentflux of98m3/s,500m3/s and1000m3/s before and after implementing the waterway regulation.The results show that with the increase of the discharge flux of Baishiyao complex, theinfluence of waterway regulation project to water level and gradient decreased gradually.After implementing waterway regulation, the chamfer velocity increase slightly. When thecontrol flow is500m3/s, the chamfer velocities of the un-connecting tail section and varyingbackwater zone are higher than the sediment-moving incipient velocity (D=0.55mm) and alsonot less than the velocity before implementing waterway regulation. It means that the chamfervelocities in these two zones can satisfy the velocity requirement of maintaining the chamfer stable. But the small velocity of perennial backwater zone may lead to sedimentation inchamfer area. The sediment transport rates in both shoal section and deep groove section withthe control flow of500m3/s indicated that the sediment transport ability of varying backwaterzone is slightly higher than both the un-connecting tail section and deep groove section. Itmeans the situation will be helpful for maintaining the chamfer stable. But the weak sedimenttransport ability of perennial backwater zone may lead to the sedimentation.The results of1-D&2-D numerical simulation for flow characteristics of Baishiyaodownstream reach show that the research river can satisfy the the kiloton ship’s navigationrequirements and the waterway regulation project is reasonable, but sedimentation may existin perennial backwater zone.