Study On Width-Averaged 2-D Numerical Simulation For Tidal Flow

The water environment problem resulting from the impregnation of trade waste and sewage can't have already been neglected in estuaries and coastal area. At the same time, because of reduction of fresh water in the estuary, the seawater salinity has increased and this also causes the deterioration of the water area. The dweller's life quality is affected around the estuary ,meanwhile the comprehensive utilization of water qualityand water resources in the estuary are also affected , accordinglythe economical development of the whole estuary region is restricted, so disposal problem of the water environment have already stared us in the face and been paid more attention.The transportation of the pollutant in the estuaries and coastal area closely relates to tidal flow, so the tidal flow is firstly described quantitatively in order to research the problem above.1The researches on tidal flow are the foundation of studying transportation law of pollutants and of evaluating water environment in the estuaries and coastal area. Numerical simulation is an important approach of researching such as the problem.The main task of this paper is to adopt width-averaged 2-D numerical model to simulate tidal flow and develop the software, Specified as follows:1 Domestic and overseas research situation on tidal flow is comprehensively reviewed.2 Unsteady flow free-surface numerical simulation methods are analyzed and compared.3 On the basis of these, the control equations of water floware integrated and the variables along the width are averaged and the control equations of tidal flow based on width-averaged 2-D numerical model are obtained, consequently the two-dimensional vertical numerical model to describe movement characteristic of tidal flow is established.4 The VOF method is chosen to track free-surface flowof tide, consequently the two-dimensional vertical numerical model to describe movement characteristic of tidal flow is established. Tidal flow is described by the model built in the paper including width-averaged continuity equation andmomentum equation (N-S equation) as control equations of key flow field and using the width-averaged volume of fluid function as assistant equation.5 Finite-difference method is used to approximate thepredicting equations, The finite-difference approximation used for the continuity equation is an implicit relation , momentum equation approximation is received by a combined relation and the governing equation for the Volume of Fluid is solved by Donor-Acceptor method.6 the location and orientation of free-surface within surfacecells are related to the F values of these surface cells and the F values in the neighbor cells and the updated fluid configuration of free surface must be given at each step.7 The transmittal of the 2-D breaking bore in elevation andthe tidal movement in factual seas are simulated by the model established in the paper. And the results are compared with theoretical and experimental values respectively. It shows that the calculation results agree reasonably with the theoretical and experimental values. The computed results have higher precision and are satisfactory.