Large eddy simulation of air flow and pollution dispersion around buildings
Date
2008
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Abstract
The study of pollution dispersion in urban environment require more accurate prediction of air flow. The high Reynolds number air flow in the atmospheric boundary layer results in fully turbulent flow. Turbulent flow over three-dimensional obstacles is still challenging in engineering; however, a greater understanding of it is necessary to environment management. This work is an effort to provide a new code to simulate air flow around a few simple obstacles and predict the pollution dispersion in the atmospheric boundary layer for a single case. Simple but reliable methods and models were adopted in developing the code in C++ to numerically solve the fluid flow equations using large eddy simulation (LES). In addition, the mass transfer equation was numerically solved to predict the pollution dispersion around a cube mounted on the ground in the atmospheric boundary layer. Several cases were examined by the code for fluid flow simulation. The first and simplest simulation was conducted for a cube obstacle in the atmospheric boundary layer and was selected for the pollution dispersion case as well. A few parameters were changed for this problem to investigate the effects of the Reynolds number, grid spacing, and sub-grid scale constant on the flow patterns. The fluid flow around a cube mounted on a plane in a channel was the second problem. Finally, the fluid flow around two parallel rectangles in the atmospheric boundary layer with a little passage between them was investigated. All the results obtained from simulations were assessed with experimental data from the literature. However, the major differences between simulation setups and experimental models have been considered in the discussion. The most important difference between experiments and simulation was the approaching flow into the obstacles. Simulations were carried out by laminar inflow condition; however, in the experiments, fully turbulent flow had been used. As a result, the flow pattern was changed significantly; so that in the simulation with the laminar approaching flow, the wake behind the obstacle increased and the vortex on the roof disappeared. There is a good agreement between the simulation result and experimental data in most of the case. In fact, the flow in the channel resulted in more reliable outcome than the flow in atmospheric boundary layer. The developed code showed the capability of accurately predicting the pollution dispersion accurately with some modifications.
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Bibliography: p. 193-207
some pages are in colour
some pages are in colour
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Citation
Omidyeganeh, M. (2008). Large eddy simulation of air flow and pollution dispersion around buildings (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/2149