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Modeling the Dispersion of Vapor and Aerosol Particulates in the Atmospheric Boundary Layer

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Final technical rept. 1 May 1998-30 Apr 2001

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The goal of this project is to improve our scientific understanding of dispersion issues over complex terrain and publish results in scientific journals. Three scientific articles and one students Master thesis are under preparation based on the results supported by this project. The first paper, entitled The role of advection of fluxes on modeling dispersion in convective boundary layers, is aimed at examining the importance of the advection terms for dispersion in a convective boundary layer. An Eulerian three-dimensional higher-order closure dispersion model is presented. The model uses mean wind and turbulence values from a second order atmospheric boundary layer model. The dispersion model is validated against results from tank and field experiments and compared to results from Lagrangian dispersion models. The results show good agreement with experiment and Lagrangian modeling results for point source dispersion in a convective boundary layer. Sensitivity studies of the model helped to identify the roles that advection and horizontal transport terms in the equations for the fluxes play in simulating the essential features of pollutant dispersion. The results from the sensitivity tests show that the famous features of dispersion from a point source in the convective boundary layer - with an ascending plume during ground level release and descending for a lifted point source - is caused by the advection term in the equation for the vertical flux. Furthermore, it is shown that there is a tendency for the plume to split horizontally, which is also caused by the advection term in horizontal fluxes.

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  • Fluid Mechanics

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