Abstract

Grid resolution plays an important role in numerical hydrodynamic and transport modeling. Without an adequately high grid resolution, a numerical model will not be able to resolve important physical phenomena in areas of interest. A finite difference model can be setup for simulation using a grid with a high horizontal grid resolution at the main areas of interest. However, this high horizontal grid resolution will extend throughout the whole computational domain. This will significantly increase the computational time and memory requirements for the model. Therefore, the inset grid technique has been widely used with finite difference models to overcome these limitations.

In 2018 the 3D GSMB (Geophysical Scale Multi-Block) hydrodynamic model was used for the study of water quality and sediment transport in Mobile Bay for the calendar year 2010. This model was calibrated and validated on a global computational grid domain which stretches from Lake Pontchartrain, LA to Pensacola, FL. In 2021 the model was calibrated and validated for the calendar year 2015 under the Deer Island Ecological Restroation Project.

However, the horizontal grid resolution of this grid was very coarse at the Little Dauphin Island area. Taking advantage of model results from this study and using it as boundary conditions, an inset grid with high grid resolution at the Little Dauphin Island was generated. The 3D GSMB model once again was setup on this inset grid for conducting hydrodynamic and salinity transport studies for the Little Dauphin Island area. These studies include Drury Pass Open with a new channel design and Drury Pass Close scenarios. Model results from the 3D GSMB model on the inset grid for the calendar year 2015 will be presented.

Keywords: Grid inset, grid resolution, numerical hydrodynamic modeling, salinity transport.