A three-dimensional tidal model in boundary-fitted curvilinear grids

In hydrodynamic models of marine and estuarine currents the use of boundary -fitted curvilinear grids not only makes the model grids fit to the coastli ne and bathymetry well, but also makes the kinetic boundary conditions simp le and more accurate. Because of these advantages, a three-dimensional tida l model with boundary-fitted curvilinear grids has been developed to simula te both tide and current in estuarine and shelf water. The basic idea is to use a set of coupled sigma-stretched and elliptic transformations to map t he physical space into a corresponding transformed space such that all boun daries are coincident with co-ordinate lines and the transformed grids are rectangular. The hydrodynamic equations in the transformed space are solved in a rectangular mesh of the transformed grid system. The application of t he model in the simulation of the M-2, S-2, K-1 and O-1 tidal waves in the Bohai Sea, China, shows that the numerical results are in good agreement wi th the observations. The method of boundary-fitted curvilinear grids is eff ective for improving simulation accuracy of current in the estuarine and sh allow seas, especially at the coastal regions where the current was usually impractical by a uniform Cartesian grid system with the shoreline and bath ymetry represented by numerous stair-steps. (C) 2000 Academic Press.