A Numerical Simulation And Research On The Ocean Hydrodynamic Elements Response To Wind Fields In The Changjiang Estuary And The Hangzhou Bay

A numerical model for coastal storm surge simulation has been established to cover the Changjiang estuary and Hangzhou Bay based on the Finite Volume Coast and Ocean Model (FVCOM). FVCOM adopts an unstructured, variable resolution triangular grid and finite volume method. In the same time, the model takes the effects of astronomical tides, surface runoff and typhoons into account.A 3-D numerical tidal model for the Changjiang estuary and Hangzhou Bay is established at first, and the characteristics of the tide and tidal current have been discussed. The computed results agree with the observation well. The tidal model also laid the groundwork for storm surge simulation.Four numerical experiments model for FVCOM ideal wind simulation have been established to test the simulated wind currents.22 typhoons in the Changjiang estuary and Hangzhou Bay are statistically analyzed, and two types of typhoons which invaded directly into Changjiang estuary and Hangzhou Bay are generalized:I is landed on Zhejiang province, II is moved northward on the sea. The WRF model and typhoon model are used to simulate the wind and pressure of the typhoon. The pressure field of typhoon model is computed by used of Takahashi and Fujita T., and the wind field is by Ueno.After comparing with the observed data, the typhoon model meets the storm surge model's requirements, and it's easy to adjust. So the study adopts the result of the typhoon model as meteorological field of the storm surge.A storm surge model for the Changjiang estuary and Hangzhou Bay is established considering separately the influence of astronomical tidal, typhoon (TC9806 and TC0012) and their coupling. The set-up and set-down of local water level are impacted by the intensity and the path of the typhoon. The variety of single point of the surface sea current under the three conditions is more obvious than the bottom one; the single point of flow direction under storm takes on the periodic variation still, and the difference happened only when typhoon arrives, it shows the important effect of the astronomical tidal in the Changjiang estuary and Hangzhou Bay; the distribution of the sea surface current is influenced by the intensity and path of the typhoon, and some small circulations appear at local small area under the typhoon and topography's combined action. The oceanic momentum which caused by typhoon transferring downwards can get to the bottom of the sea. The coastal residual water elevation was influenced remarkablely by typhoons, and the effect of storm surge can make a set-up nearly 1m. The surface residual currents generate the jet which mainly repose to the strong wind of typhoon and the jet speed could get 1-1.5m/s. The biggest gradient of residual current in vertical section happens at shallow waters about 5-6m in deep.