الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
High pollution levels are often observed in urban street canyons due to increased traffic emissions and reduced natural ventilation. In recent years, many researches have been conducted to study the influence of buildings and other urban structures on air now patterns and pollutants dispersion in street canyons. Due to the rapid development of computer technology and, Computational Fluid Dynamics (CFD) modeling, numerical analysis becomes a valuable tool in studying air flow and pollutants dispersion around buildings.
This study is concerned with studying the air flow and pollutants dispersion in street canyons. To achieve this goal, one needs a good computer code, an accurate numerical model, and a grid with a sufficient resolution to capture the small gradients.
The numerical model used in the simulations is based on an Eulerian-Lagrangian approach. The carrier phase ”air” is treated by an Eulerian modeling approach, while the dispersed phase ”pollutant” is handled by a Lagrangian model.
A second order accurate finite-volume scheme is used to solve the Reynolds averaged Navier-stokes equations. The study examines the perforn1ance of five Reynolds¬averaged turbulence models namely; standard k-e model, RNG k-c model, realizable k-c model, standard k-w model, and Reynolds Stress Model (RSM) in simulating the air flow patterns ”zones” around an isolated building in turbulent atmospheric boundary layer. The results of all turbulence models are compared with the available experimental data to select the best model whose results have the best agreement with the experimental results.
The study extends to simulate pollutants dispersion in street canyons using the Eulerian model with the selected turbulence model coupled with the Lagrangian model. The results are compared with the corresponding experimental data and previous numerical results to validate the CFD model.
The comparisons show that the Reynolds Stress Model (RSM) coupled with the Lagrangian model is rather promising to study air flow and pollutants dispersion in street canyons.
The study investigates the effects of street canyon configuration on air flow patterns and pollutant dispersion within the canyon region to determine the configuration which has the best natural ventilation for the canyon. The results show that the avenue street canyon is the best street canyon configuration in terms of natural ventilation.