摘要：Air pollution is considered one of the main challenges of environmental sustainability. Metropolises are increasingly facing the problem of air pollution, which seriously affects people's health. There are several factors associated with air pollution in the streets including urban form, ventilation, and air pollution sources. In the present research, the effects of the street canyon direction on the wind behavior and pollutant dispersion have been investigated using CFD and the model has been validated with the wind tunnel.The results show that, the orientation of the urban canyon affects both airflow and air pollutant dispersion patterns. In F3 (α =90°), where the wind direction is perpendicular to the street, ventilation is mostly through the street roofs, so that the amount of pollutant in the roof height is almost 183% of F2 (α=45°) and 347% of F1 (α =0°). Since near the leeward wall the velocity of airflow is decreased to zero, these spaces are highly susceptible areas for pollution accumulation. In F1, ventilation is mostly through the longitudinal displacement of pollutions and dispersion via lateral openings. In this case, the beginning parts of the urban canyon are the most well-ventilated ones, and the end of it has the highest level of pollution concentration. It was also found that the lowest level of pollution occurs in F2. Finally, the diagonal street (F2) has been recognized as the optimal direction for main streets in the residential areas of Tehran which should be taken into consideration in the Sustainable Urban Development Principles of Tehran (SUDPT).
关键词：Air pollution dispersion; Air flow; CFD; Urban canyon's direction; Iran
