Numerical simulations of the effect of building configurations and wind direction on fine particulate matters dispersion in a street canyon

To explore the effect of traffic emissions on air quality within street canyon, the wind flow and pollutant dispersion distribution in urban street canyons of different H/W, building gap and wind direction are studied and discussed by 3D computational fluid dynamics simulations. The largest PM_2.5 concentrations are 46.4, 37.5, 28.4 µg/m³ when x = ? 88, ? 19.3, ? 19.3 m in 1.5 m above the ground level and the ratio of H/W is 1:1, 1:2 and 2:1, respectively. The flow around the top of the building and clearance flow between the buildings in street canyon influence by different H/W, which affected the diffusion of fine particulate matters. The largest PM_2.5 concentrations are 88.1, 31.6 and 33.7 µg/m³ when x = 148.0, ? 92.3 and ? 186.7 m above the ground level of 1.5 m height and the building gap of 0, 20 and 40%, respectively. The air flows are cut by the clearance in the street canyons, and present the segmental characteristics. The largest PM_2.5 concentrations are 10.6, 11.2 and 16.0 µg/m³ when x = 165.3 m, x = 58.0 and 1.5 m above the ground level of 1.5 m height and wind direction of the parallel to the street, perpendicular to the street and southwest, respectively. Modelled PM_2.5 concentrations are basic agreement with measured PM_2.5 concentrations for southwest wind direction. These results can help analyze the difussion of PM_2.5 concentration in street canyons and urban planning.