Modeling gravity currents in shallow bays using a sigma coordinate model

Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732Capturing the physics of thin underflows in hydrodynamic models is a challenge when modeling large-scale environmental systems, as the computational time associated with the use of fine vertical grid resolution often leads to under-resolution of gravity currents. In the present work, the impact of vertical grid resolution on both hydraulic and transport phenomena in the sigma coordinate model EFDC are examined. Vertical grid resolution is varied in simulations of a 2D gravity current in a basin scaled on a shallow bay, Corpus Christi Bay in Texas, USA, that is affected by the adjacent hypersaline Oso Bay. The simulations are run with and without a turbulence closure in order to quantify numerical and modeled entrainment. Entrainment rates and Froude Numbers are compared at different vertical grid resolutions, and the range of resolution over which results are not grid dependent is identified. A minimum resolution for accurate gravity current modeling is recommended for future gravity current modeling in EFDC