Three-Dimensional Numerical Simulation Of Dynamic And Sediments In Changjiang Estuary In Dry Season

By creating a large scale computing grid (south to Kanmen, north to Lianyun Harbor, west to 125.15°E )of Changjiang estuary and Hangzhou Bay and their neighboring sea areas and using up to date data of tidal stations, 8 major tidal constituents, M2, S2, N2, K2, K1, O1, P1 and Q1, are simulated more accurately. And thus more accurate tidal level boundary condition can be given at the open boundaries of models of Changjiang estuary. Based on well simulation of 8 major tidal constituents in large scale, the data of synchronous observation of February, 2003 is compared and a grid including only Changjiang estuary is created for validation of hydrodynamic numerical simulation in Changjiang estuary and analysis of flow field. Residual current and overall residual are simulated under individual effect of each dynamic factor. The character of each residual constituent and the contribution of each to overall residual are analyzed. To simulate the suspended sediments of Changjiang estuary, a 3-D mathematical model of suspended sediments with the combine effect of wave and current is set up. In the model, the wave parameter is computed by use of the famous third generation shallow water wave model SWAN, the source function of the sediment in the convective diffusion term is determined by the shear stress, which is most clear in physics. In addition, a surface boundary layer model is used here to concern the influence of the wind wave to the shear stress at surface, a bottom boundary layer model to concern the variation of bottom shear stress under the combine effect of wave and current. The radiation stress is added to the right side of the governing equation to concern the momentum flux generated by wave. The surface boundary condition of the turbulence closure model is revised to concern the wave turbulent flux and the influence of salinity and sediment concentration towards the sedimentation velocity of suspended sediment. The influence of wind wave to estuarine maximum turbidity zone is studied by constructing an ideal estuary and using 3-D suspended sediment model. Moreover, the suspended sediment model is applied to Changjiang estuary, and the wind wave, salinity and suspended sediment in dry season of Changjiang estuary are simulated. The computing results at surface and bottom layers during neap tide and spring tide are compared with the observed data. The analysis of the computing result of suspended sediment is also carried out in this paper. It shows that the model can perform good simulation of suspended sediment of Changjiang estuary.