Abstract
Using the Computational Fluid Dynamics technique (CFD), we explored the effects of the atmospheric stability conditions on the dispersion of solid and gas-phase pollutants emitted from an area source located on a flat region. As an application, the dispersion of pollutants emitted from roads located on flat terrains was considered. Toward that end, we set up a model that describes the dispersion of air pollutants in a small region (< 1 km long) near the ground surface (< 250 m high). It consists of a neutrally stratified model modified to account for the atmospheric stability effects by imposing the near-ground stratification through the Monin–Obukhov similarity theory and the k–ε turbulence model adjusted for each atmospheric stability condition. Using this model, we simulated the dispersion of pollutants emitted from the road and plotted the resulting downwind concentrations in terms of dimensionless numbers. Results from our CFD-based model were highly correlated (R2 > 0.95) with the SF6 concentrations measured downwind a line source of this trace gas by the U.S. National Oceanic Atmospheric Administration in 2008 under different conditions of atmospheric stability. Numerical and experimental results showed that, under any of the stability conditions explored, the near-road pollutant concentrations are highly correlated (R2 > 0.87) to the concentrations observed under neutral conditions. When the atmosphere is extremely stable, those concentrations were up to 12 times higher than those observed under neutral conditions. We report the constant of proportionality obtained for every stability condition.
Highlights
Using the Computational Fluid Dynamics technique (CFD), we explored the effects of the atmospheric stability conditions on the dispersion of solid and gas-phase pollutants emitted from an area source located on a flat region
When the atmosphere is under extremely stable conditions (0 < L < 20) fs varies with L and reached values of up to fs = 12
This work aimed to evaluate the influence of the atmospheric stability on the dispersion of pollutants emitted from an area source over a flat surface without any obstacle to the free wind flow
Summary
Using the Computational Fluid Dynamics technique (CFD), we explored the effects of the atmospheric stability conditions on the dispersion of solid and gas-phase pollutants emitted from an area source located on a flat region. We set up a model that describes the dispersion of air pollutants in a small region (< 1 km long) near the ground surface (< 250 m high) It consists of a neutrally stratified model modified to account for the atmospheric stability effects by imposing the near-ground stratification through the Monin–Obukhov similarity theory and the k–ε turbulence model adjusted for each atmospheric stability condition. Environmental authorities and the scientific community are looking for micro-scale range models (~ 1 km) based on computational fluid dynamics (CFD) to evaluate the influence of the atmospheric stability conditions near the ground surface (~ 250 m) on the dispersion of pollutants from area sources like:. According to the Pasquill–uifford stability classification classes D applies to heavily overcast skies, at any wind speed day or night
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