Development And Application Of The Coupled Model Of The River Networks And Estuary

The Pearl River Delta networks and the Lingding Sea area are an integer with intense water-sediment exchange. Therefore, based on the existing researches, a 1-D and 3-D coupled numerical model is set up which takes the Pearl River Delta and the Lingding Sea as one part and studies the dynamic distribution characteristics of water, sediment and salinity.This dissertation first establishes the 1-D numerical model of the Pearl River Delta networks using the "junction control method for water level" and the "junction control method for sediment concentration". Then the 3-D flow field and the suspended sediment field numerical model under the σ coordinate are built. The vertical eddy coefficient is obtained with the K-KL two equation turbulence closue model. Considering the density baroclinic effect caused by the salty water invasion, the salinity field computation is added in the hydrodynamic model to make the vertical velocity distribution better representing the practical situation. In the suspended sediment field numerical model, the bottom shearing stress is computed to supply the bottom boundary condition and the suspended sediment concentration through aggradations and re-suspension supply the water and sediment exchange. In the material transportation equation computing temperature, salinity and suspended sediment, the interpolation method is modified to improve the computing precision of the horizontal diffusion term and to decrease the numerical dissipation and instability occurring in the computation so that it can be applied to the case of more intensive bottom slope. The additional hydrodynamic equation of the 1-D and 3-D coupled numerical model is derived and the 1-D and 3-D boundary conditions on the connecting section are satisfied through iteration. The continuity of the material transportation is guaranteed by the connection of the suspended sediment and the computation is accomplished by the inter-transportation of the sediment concentrations of 1-D and 3-D models.In the dissertation the current diversion ratio, the sediment diversion ratio and the flow profiles of the main junctions in the Pearl River Delta networks are studied to state the macro law of the Pearl River Delta. The relationship between the northwest river and the east river is proposed under different hydrographic settings by the judgment of the interactions of the two rivers. In the Lingding Sea area, the inter-relationships between velocity field, salinity field and sediment field are analyzed in detail by studying the flow profile, the salinity distribution and the sediment transportation of the vertical and horizontal sections of the eastern and western deep pools.