A Three-Dimensional Unstructured Cartesian Grid Model for Crystal River/Kings Bay in Southwest Florida

A three-dimensional hydrodynamic model using unstructured Cartesian grids has been developed for an estuarine system called Crystal River/Kings Bay in southwest Florida. The 3D model uses a cut-cell approach to fit the bottom topography and shorelines and solves flux-based finite difference equations using an efficient semi-implicit method. At the same lime, the model has the ability of discretizing complex geometries with Cartesian grids that can be liberally downsized in the two horizontal directions. With the help of a geophysical information system, the grid generation process is quite straightforward and does not suffer the grid generation headache often seen in other unstructured models, because the unstructured Cartesian model does not require grids to be orthogonal. This allows the arrangement of model grids to be very flexible, as any of the Cartesian grids can be split into two without affecting its surrounding grids. The newly developed model was validated with a couple of test cases in rectangular basins, before it was qualitatively tested for the Crystal River/Kings Bay system. Model tests show that the unstructured Cartesian grid model works well in these shallow water cases.