Study On Numerical Simulation Of Hydrodynamic And Sediment Transport In The Yangtze River

The Yangtze River carries a large amount of sediments when entering the sea.The hydrodynamic forces reshape the estuary topography and its evolution,during which process the sediment is a pivotal link between hydrodynamic forces and geomorphological evolution,while hydrodynamic action is the direct cause of suspended sediment transport,sedimentation and resuspension.However,in recent years,under the background of more and more human activities such as the Three Gorges Dam and the South-to-North Water Transfer Project,the runoff and sediments from the Yangtze River into the sea have been significantly reduced.Along with this phenomenon,the hydrodynamic forces of the Yangtze River into the sea and the sediment transportation must change.Therefore,the paper focus on the study of the interaction between water and sediment in order to have a better understanding of water flow and sediment transport characteristics which can reveal the evolution of the silt bed in the Yangtze River estuary,thus providing a scientific basis for the solutions of the Yangtze River estuary's water environment and pollutants as well as for the coast.Besides,it can also provide strong technical support for waterway engineering construction.This paper uses the Delft3 D sediment transport model to simulate the sediment transport process in the Yangtze River Estuary,and then utilize the data obtained in July 2016 to verify the velocity,direction and suspended sediment concentration.The verification results show that,except for some individual mutations,the overall results are in good agreement.The model can better reflect the interactions between wind,topography,Yangtze River runoff,and the tidal currents there.It is sufficient to accurately simulate the tidal hydrodynamic force in the Yangtze River Estuary and the sediment transportation.In the subsequent control experiments,the influences of wind,topography,Yangtze River runoff,and tidal currents on the flow field and sediment transport mechanisms were mainly analyzed.The experimental results show that the wind has a small inhibitory effect on the dispersion of sediment,but it will make the sediment concentration at the observation sites larger;after removing the M2 tide,the range of sediment diffusion has greatly reduced so that the suspension sediment concentration at the observation sites is basically 0,and evidence indicates that the tide that is the driving force of the boundary has the greatest impact on the transport process of sediment;the decrease of the Yangtze River runoff leads to a less spread in the northeast direction for the sediment transportation;the terrain is not an independent factor,mainly because it will influence the boundary condition of other factors such as wind,Yangtze River runoff,and the tidal currents and their effects on the sediment transport process.From the results alone,the reduction of the topography will make the eastward transport of the sediment to a larger extent and concentration.