Effects of Structures on Toxic Vapor Dispersion.

Abstract : Currently available toxic vapor dispersion models at Air Force facilities do not adequately include the effects of structures on the rate of dispersion. Some relevant models and data sets are available in the literature as a result of research by other organizations. This literature was reviewed and an assessment made of the feasibility of producing a viable modeling system. It is found that increases in concentrations due to the confining effects of structures are significant relative to overall dispersion model uncertainty. A framework for a microcomputer-based modeling system is proposed that accounts for aerodynamic effects around one building or groups of structures, including downwash vapor and vapor trapping. Both neutrally-buoyant and dense gas cases are considered, and the model is constructed such that it is capable of a smooth transition to other dispersion models at downwind distances where the effects of the structures become significant.