Date of Award

1993

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

First Advisor

Danny D. Reible

Abstract

Due to the complexity of some buoyancy driven atmospheric flows, it is sometimes not possible to accurately predict pollutant transport on the basis of sparse wind field measurements. A possible solution is mathematical modelling of both the flow and pollutant transport. In order to overcome shortcomings of the conventional E-$\epsilon$ model such as defining proportionality coefficients (c$\sb{\rm m},$ c$\sb{\rm h})$ and to develop a more general model of stratified environmental flows, a modified E-$\epsilon$ model was proposed through use of the algebraic stress model including wall proximity effects. The resulting model was compared herein to data and higher order simulations in stable, neutral and convective atmospheric boundary layers (ABL). The modified E-$\epsilon$ model reproduced well the observed behaviors. The modified E-$\epsilon$ model with full nonhydrostatic equations was applied to a sea breeze circulation. The key characteristics of the sea breeze, such as development of a daytime onshore flow, deep inland penetration of the breeze in late afternoon, frontal development in late evening, thermal internal boundary layer (TIBL) and fumigation in the TIBL were reproduced. The residual plume over the sea showed great impacts on the ground level concentration during the following day sea breeze and it should be considered in the estimation of pollutants near the coastal region. All the plume emitted from an elevated line source during the nighttime offshore flow also returned back to the land with the subsequent afternoon sea breeze. The modified E-$\epsilon$ model was also used to estimate the dispersion of pollutants by a "thermal fence" under neutral and stable conditions. A line of heaters or a thermal fence has been proposed as a means of reducing ground level concentrations near area source such as a landfill under nighttime stable condition. It was proved that the thermal fence with the relatively small heating rate enhanced the dispersion of the pollutants behind it by increasing the vertical mixing under the neutral and stable conditions.

Pages

227

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