Improvement of a coastal current computation model based on dual-sigma coordinate system and GAL model

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(1) Developments of Coastal Current Simulation Models : We developed a numerical model based on GAL model to calculate coastal front evolution in a reasonable manner and verified its fundamental performance. We applied this model to simulate dynamic behavior of saline front of a river plume. Besides we have attempted to improve a coastal current simulation model by introducing the dual-sigma coordinate system, which has been developed by Nadaoka et al. (2000), into the scheme of POM, and coupling with RAMS to reasonably evaluate a regional wind field. As an application we performed numerical simulation for Manila Bay, which is highly polluted. On the other hand we developed SDS-Q3D, on the basis of SDS-2DH model by Nadaoka and Yagi (1998), for turbulent flow computation in shallow water like coral reef, sea grass bed and tidal flat. We further extended SDS-Q3D model by incorporating the effects of density stratification and partial drying-up of the computational region at low tide to e … More nable the computations of, e.g., density currents over tidal flat near a river mouth. We developed also a non-equilibrium material transport model, which may be easily coupled with the SDS-Q3D model. These models are based on a spectral method, and have remarkable advantages that they can be applied to arbitrary bottom topography and are free from vertical numerical diffusion.(2) Development of a New Nesting Method : As a reasonable way to handle an open boundary problem for coastal current computation in wide area, we have developed a new nesting method in which larger scale computational results are reflected on smaller scale computations through entire grid points, although in the previous methods larger scale results are reflected only through boundaries of smaller scale computational domain.(3) Field Surveys and Laboratory Experiments : For obtaining data of currents and others for validation the coastal current simulation model developed in the present study, we performed field observations at the coastal area in the southwest of Okinawa Island, which is open to the surrounding oceans. Less