Study On Flow And Sediment Based On ADCP And Its Application In 3-D Numerical Model In The Yangtze River Estuary

The purpose of this dissertation is to study the movement law of water flow and sediment in the Yangtze River Estuary based on measured data of water flow obtained from ADCP and of suspended sediment from the field samples, in a 3-D numerical model of water flow.According to the characteristics of estuarine tidal current, its movement law in the Yangtze River Estuary is studied by analyzing measured data of water flow obtained from ADCP. First of all, the basic principle and method for the application of ADCP are introduced, and then its error control is discussed, and the post treatment methods of its measured data are studied in detail as well. Using ADCP and the related knowledge of hydrology, sediment kinetics mechanics, river kinetics mechanics and mathematical statistics, the law of tidal current in the Yangtze River Estuary is studied. Based on the characteristics of estuarine tidal current, the mechanism of forming water flow circulations in the Yangtze River Estuary is researched as well as the main affecting factors. The main causes of circulations are the Coriolis force brought by the Earth rotation itself, the interaction of runoff and tidal current, and the density gradient caused by saltwater intrusion.The measured data of discharge from ADCP are treated in three different methods and the discharge distribution law of transect in the Yangtze River Estuary is obtained. The results show that the distributions of discharge passing unit width area are basically consistent with the shape of river transverse cross-section whereas the variation of river topography affects discharge distribution obviously. To a certain extent, the distributions of discharge passing unit width area can indicate the interaction relationship between tidal current and river boundary, the momentum magnitude of water volume passing unit width area, the intensity of water flow, and straightly water flow dynamic action on riverbed.Based on measured data of water flow obtained from ADCP and of suspended sediment, suspended sediment movement in the Yangtze River Estuary is studied. Results show that they are identical in the modes of suspended sediment and water flow with three sediment circulation modes in the Yangtze River Estuary as well. Where the interaction between runoff and tidal current counterbalances relatively, there exists three sediment circulation modes, the longitudinal sediment circulation that the upper layer sediment transports to sea and the lower layer sediment to inland, the horizontal sediment circulation that northern side sediment transports to inland and southern side sediment to sea, and the transversal sediment circulation that theupper layer sediment transports to southern and the lower layer sediment to northern. Relationship between tidal discharge and sediment discharge is also analyzed here.Using a 3-D numerical model of tidal current with orthogonal curvilinear co-ordinates, tidal current in the Yangtze River Estuary is calculated. Besides regular verification methods such as tidal level, velocities at fixed points and of vertical lines, ADCP's measured data are herein used to verify calculated data, including velocities and discharges at transverse cross-sections. The interrelation degrees between surveyed velocities and calculated velocities are verified. The result shows that the numerical data are in good agreement with the measured data.