Comparison of an accidental release modeling technique with recent spill test data

The use of mathematical models to evaluate and analyze the consequences of a hazardous spill, has become a crucial part of Emergency Response and Planning. Simple models for the evaporation and subsequent dispersion of the cloud serve a useful role for screening purposes. However, to model realistic scenarios one has to design a comprehensive system capable of handling various situations. In this paper the authors focus on one aspect of the complete spectrum of scenarios. They attempt to study the instantaneous release of a heavier-than-air gas. It has been argued that this scenario does not truly reflect a real-life situation and is most unlikely to occur. However, some precise trials have been conducted where large quantities of heavy gas were instantaneously released and these provide an excellent data base for evaluating and testing the assumptions made by a model. They describe a simple box-model that can take into account the effects of gravity slumping, ground heating and has a very simple entrainment formulation. They use this model to compare with real-life trials conducted at Thorney Island and Porton Downs. The exercise of simulating these trials illustrate the complex phenomena that actually occur during a release, and highlight the limitations ofmore » predictions due to inherent model assumptions.« less