Browsing by Author "Ali, Ahmada Omar"

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    Modelling the dispersion of atmospheric pollutants using two dimensional advection diffussion equation
    (University of Dar es Salaam, 2011) Ali, Ahmada Omar
    This work focuses on the development of two dimensional advection-diffusion equation and use it to model atmospheric pollutant dispersion in the effort to study the behaviour of the dispersion of pollutants in the air A two dimensional atmospheric dispersion mathematical model for computation of the ambient air concentration of reactive emitted from ground ]eve] sources is described. The advection-diffusion equation uses meteorological data obtained form the literatures to model air pollutants dispersion. The model is presented in form of partial different equation (pde). Different pollutants, how- ever, may present different variability characteristic due to their specific emission patterns, rates of diffusion, depth and transformation behaviours like atmospheric reactions. The study of pollution transport phenomena using the advection- diffusion equation was done in three consecutive steps. Firstly we derived the advection-diffusion equation from physio-chemical laws governing the transport phenomena and discuss its properties together with initial and boundary conditions. Secondly we discretized the Advection- Diffusion equation and suggest a positive difference method to solve numerically a two dimension Advection- diffusion equation. Lastly we tested the method to generate approximate numerical solutions simulating different scenarios of pollution transport in a two dimensional domain. The outputs presented in graphical form that like other parameters, depth has significant influence on the dispersion of pollutants. The drift velocity of air moves the polluted zone from one region to another at the rate which is proportional to its magnitude. The eventual chemical reaction between the pollutant, the depth and one or more air components acts as a pollution sink or fall out and hampers the horizontal expansion of polluted zone.