CFD modeling of dense gas cloud dispersion over irregular terrain

Numerical calculations were performed to reproduce the transport and dispersion of the instantaneous release of finite volumes of dense gases over homogeneous flat, sloped, and complex terrain surfaces for calm and windy situations. The 1981 Porton Trial Test 8 field study of the release of 40 m3 of a Freon-air mixture was used as a validation case to evaluate the behavior of volume integrated, cross-section integrated , depth integrated and full 3-d CFD models. In addition wind-tunnel measurements by Meroney & Lohmeyer (1983, 1984) about an instantaneous cloud of dense gas released in a wind were reproduced by similar calculations. All results were inter-compared, and time-dependent cloud dimensions, arrival times, and concentrations were considered. Very similar behavior was found for all models which tend to validate all methods as useful predictors.

► Numerical models replicate dense gas cloud field and laboratory experiments over flat terrain. ► Calm and windy dispersion for flat terrain are reproduced by all numerical models. ► Models replicate gravity driven flows including downslope transport and gravity head development. ► The CFD solutions provide increased spatial resolution and temporal details of the dispersion process. ► Models examine transient plume characteristics often seen in the field but difficult to measure.