Reducing the pollution concentration on the urban street ventilation is significant for creating a healthy urban living environment. In this study, the effects of source location on airflow patterns and pollutant transmission in street canyons under the influence of wind and thermal buoyancy forces have been investigated using the CFD approach. Also using the RNG k-ε model, RANS equations, and the Boussinesq model the structure of airflow, thermal behavior, and dispersion of pollutants in a deep street canyon in three-dimensional space have been evaluated. The results show that the combined effect of wind force and buoyancy effect enhances air circulation and turbulence of air layers in street canyons; the source location of pollution in a street canyon can significantly alter the distribution and concentration of pollution in the canyon. Sunward sides, as a thermal plume, transport pollutants vertically to the windward area; the impact of wind force also profoundly complicates transmission pathways of pollutants. Since the pollution sources in this study are the buildings around the street canyon, the findings of the present study can improve the understanding of patterns of pollution distribution in street canyons and be useful in developing design standards for high-rise buildings in dense urban areas.
