Preliminary Study On The Flow And Sediment Flux Exchange Characteristics Between Changjiang Estuary And Hangzhou Bay

Due to the existence of compact flow and sediment flux exchange between Changjiang estuary and Hangzhou bay, the 2D numerical sediment model in orthogonal curvilinear coordinate system is built in this paper. Based on the model, the characteristics and mechanism of flow and sediment flux exchange are analyzed and discussed.In the numerical model, DSI and Euler-Lagrange methods have been introduced in the numeration of flow module and sediment module respectively. Based on the least square method, a new method called enumeration method has been used firstly in this paper. The method is different from the normal method, which makes a regression analysis after logarithm. The error analysis and result comparison show the coefficients determined by the enumeration method are more reasonability and that the results of formula are more accurate in calculating the natural sediment -carrying capacity of flow.The different effluent factors on flux exchange between Changjiang estuary and Hangzhou bay have been discussed in this paper. Based on the analysis on tidal current energy and wave action, the characteristics that the sediment on Nanhui shoal will silt in flood season and be eroded in dry season have been explored preliminary. Through the comparison between Euler residue and Lagrange residue around Nanhui shoal, the phenomena that sediment from Changjiang river will be sent to Hangzhou bay and the existence of north-south direction sediment transportation pathway near Nanhui shoal has been verified.Through the analysis on Lagrange residue on Nanhui shoal, the existence of dividing line on which has been advanced. The relationship between Nanhui shoal and Nan-slot and that between Nanhui shoal and the north part of Hangzhou bay have been discussed. The main flow and sediment exchange pathway near Nanhui shoal and the predominant range of sediment transportation in the north of Hangzhou bay have been researched.Finally the model has been used in Nanhui control engineering and Meimaosha ecological reservoir engineering , the effluences of engineering on Changjiang estuary and Hanghzhou bay have been analyzed ,the conclusion is made that the sediment flux from Changjiang estuary to Hangzhou bay will be reduced and the erosion will occur in the north part of Hanghzou bay .