Modeling Local and Advective Diffusion of Fuel Vapors to Understand Aqueous Foams in Fighting Fires

The purpose of this project was to investigate fuel vapor suppression by aqueous film and foam layers. Immediately after application, aqueous film and foam layers have the effect of suppressing fuel evaporation, however this suppression is not constant over time. If enough time elapses, the fuel vapor concentration above the film and foam layers can reach levels characteristic of an uncovered fuel pool. This can allow for reignition of the original fire. Experiments done by Leonard and Williams have studied this phenomena. It is unknown how the fuel moves through the film or foam layers and the purpose of this project was to model that movement by assuming that the fuel dissolves and diffuses through the aqueous layer. In addition to delivering a model that can simulate these experiments, I promised that this model would be capable of finding an effective diffusion constant DF for the foam and film. This would be done by minimizing the residual between the experimental and numerical results. In order to ensure that the model was correctly simulating the experiments, the model was extensively validated. After validation, the model was applied to test cases and film layer data collected by Leonard. After analyzing the results of simulating Leonard’s experiment, it appears that the dissolution and diffusion transport mechanism is not the primary transport mechanism of fuel through the film layers.