Development of a coastal fumigation model for continuous emission from an elevated point source and a computer software (Fumig)

Nazir, Muddassir (2004) Development of a coastal fumigation model for continuous emission from an elevated point source and a computer software (Fumig). Masters thesis, Memorial University of Newfoundland.

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Abstract

A fumigation model based on probability density function (PDF) approach is presented here to study the dispersion of air pollutants emitted from a stack on the shoreline. This work considers dispersion of the pollutants in the stable layer and within thermal internal boundary layer (TIBL) proceeds independently. The growth of TIBL is considered parabolic with distance inland and turbulence is taken as homogeneous and stationary within the TIBL. Dispersion of particles (contaminant) in lateral and vertical directions is assumed independent of each other. This assumption allows us to consider the position of particles in both directions as independent random variables. The lateral dispersion distribution within the TIBL is considered as Gaussian and independent of height. A skewed hi-Gaussian vertical velocity PDF is used to account for the physics of dispersion due to different characteristics of updrafts and downdrafts within TIBL. Incorporating finite Lagrangian time scale for the vertical velocity component, it is observed that it reduces the vertical dispersion in the beginning and moves the point of maximum concentration further downwind. Due to little dispersion in the beginning, there is more plume to be dispersed causing higher concentrations at large distances. The model has considered Weil and Brower's (1984) convective limit to analyze dispersion characteristics within TIBL. The revised model discussed here is evaluated with the data available from the Nanticoke field experiment on fumigation conducted in the summer of 1978 in Ontario, Canada. The results of the revised model are in better agreement with the observed data, as compared to other available models. The study suggests the use of mean absolute error and mean relative error as quantitative measures of model performance along with the residual analysis. For easy and effective use of the newly developed model, user-friendly computer software 'Fumig' is developed in visual basic. Fumig is built upon the developed model and enable easy assessment of concentration profiles under fumigation conditions.

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