Recent upgrades and enhancements of the FEM3A model

In 1984, the US Army Edgewood Research, Development and Engineering Center began to fund Lawrence Livermore National Laboratory to further develop FEM3, a fully three-dimensional heavy-gas dispersion model, as a research tool for studying the atmospheric transport and diffusion of certain chemical systems. As a result, a significantly improved version of the model, called FEM3A, was delivered to ERDEC in 1988. During the past few years, two more major improvements have been developed and tested. They are: improved mass conservation for treating dispersion scenarios with large density variations, and the addition of an advanced turbulence submodel based on the k-{var_epsilon} transport equations. These enhancements have resulted in substantial improvements in the dispersion simulations of heavy-gases and can greatly extend the range of applicability of the model, including the ability to treat problems with large density variations and dispersion scenarios of much greater complexities. Documented in this report are the new features and some of the improvements obtained with the new model