• Journal of Korean Society for Atmospheric Environment
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• v.21 no.5
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• pp.537-545
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• 2005

A new dispersion model for dense gas is constructed in the Lagrangian framework. Prediction of concentration by the proposed model is compared with measure data obtained in the experiment conducted in Thorney Island in 1984. Two major effects of dense gas dispersion, gravity slumping and stratification effect, are successfully incorporated into LDM (Lagrangian dense gas model). Entrainment effect is naturally modelled by introducing stochastic dispersion model with the effect of turbulence suppression by stratification. Not only various releasing conditions but also complex terrain can be extended to, although proposed model is appropriate for flat terrain.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.1
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• pp.73-84
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• 2006

Hazardous Air Pollutants (HAPs) are characterized by being relatively heavier and denser than that of ambient air due to the various reasons such as higher molecular weight, low temperature and other complicated chemical transformations (Witlox, 1994). In an effort to investigate transport and diffusion from instantaneous emission of heavy gas, Lagrangian Particle Dispersion Model (LPDM) coupled with the RAMS output was employed. Both deposition process and buoyancy term were added on the atmospheric diffusion equations of LPDM, and the locations and concentrations of dense gas particle released from instantaneous single point source (emitting initially for 10 minutes only) were analyzed. The result overall shows that adding deposition process and buoyancy terms on the diffusion equation of LPDM has very small but detectable effect on the vertical and horizontal distribution of Lagrangian particles that especially transported for a fairly long traveling time. Also the slumping of dense gas can be found to be ignored horizontally compared to the advection by the horizontal wind suggesting that it was essential to couple the Lagrangian particle dispersion model coupled with the RAMS model in order to explain the dispersion of HAPs more accurately. However, during the initial time of instantaneous emission, buoyancy term play an important role on the vertical locations of dense particles for near surface atmosphere and around source area, indicating the importance of densities of HAPs in the beginning stage or short duration for the risk assessment of HAPs or management of heavy vapors during the explosive accidents.