Modelling of astronomical tide and storm surge in estuary
PublisherUniversity of Aberdeen
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One objective of this project is to set up a two-dimensional model for exploring the flushing process of trapped saltwater subject to upstream freshwater turbulent flow. The multiphase Eulerian model, a part of commercial code FLUENT6.2, has been applied for the first time to study this complex mixing interaction in estuary. The distinguishing characteristic of this model is to treat saltwater and freshwater as two single miscible phases instead of a mixture phase with density variation, and the advantage of using a multiphase approach over a single-phase model is that it can efficiently and accurately treat both the free water surface and relatively high density excess between two fluids simultaneously. The other objective of this project is to develop a three-dimensional model based on the FVCOM open source code, with the aim to better understand the estuarine hydrodynamics with or without the presence of typhoon. It is found that the original FVCOM code can not reproduce an accurate tidal hydrodynamics in estuary. An improved simulation of the bed friction has been incorporated into the existing code for estuarine tide. This model has also been developed by including air-pressure gradient term to study the hydrodynamic response to cyclonic typhoon. To include the effect of typhoon (wind stress and pressure deficit), a symmetrical cyclone model is adopted. However, the typhoon-induced wind field has been predicted poorly when the typhoon enters the near-shore region. This is because the typhoon quickly loses its symmetrical property in the near-shore region. To overcome this difficulty, an asymmetrical cyclone model is derived on the basis of characteristic isobar. The accuracy of open sea boundary for storm surge model has also been improved by using large scale model. Comparison results show a good agreement with numerical simulations and physical measurements.