Various physical phenomena affecting LNG vapor dispersion were observed in LNG spill experiments conducted by the Lawrence Livermore National Laboratory. Understanding the phenomena is necessary in predicting the size of the hazardous region of vapor concentration following a spill. Gravity flow of the cold dense vapor increased cloud width while density stratification and heat flow from the ground had substantial effects on the mixing rate with air. Density stratification inhibits turbulent mixing while heat flow into the cloud promotes it through a number of processes including buoyancy. Some possible instances of buoyancy were observed in the experiments, and calculations indicate that modest amount of additional heat might substantially increase cloud dispersion. In the experiments, these phenomena led to a dependence of the maximum distance ℒ to the lower flammability limit on source rate, wind speed, and atmospheric stability that was substantially different from the prediction of the Gaussian plume model. Including these phenomena in predictive models is important for their accuracy. Time-dependent features of the concentration field due to turbulence and rapid phase-transition explosions, which also affect ℒ, were examined by applying a space-time interpolation scheme to the concentration data.

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