Investigations On The Spatial Distribution Of Particle Pollutant Concentration Near Buildings

With the increasing in urbanization and industrialization in China, air quality in the living and working environment has received more and more attentions. As the residential zones near buildings are very important for human activities, the air quality of the microenvironment of the zones has great impact on both human health and indoor air quality.In order to explore the flow field features and the distributions of ambient aerosol particles near building complexes, the flow field and the particle (i.e., 1.0μm, 2.5μm, 5μm, 10μm and 20μm) concentration distribution in the residential zones of courtyard and unenclosed buildings were simulated and investigated by employing a computational fluid dynamic(CFD) code, and the effect for avoiding particle pollution in the inner zones by two different type buildings were discussed and evaluated.The numerical results indicate that both of the courtyard and the unenclosed inner zone can decrease particle pollution from the outer space; the larger the particle size is, the higher the concentration is in the inner zone. However, the average concentrations at the breathing level and the spatial distribution features of particles in the two types of zones are not the same.In the courtyard, the deposition patterns of larger particles are dominated mainly by gravitational sedimentation, while the transport of fine particles is affected by turbulent diffusion. On the contrary, in the block of unenclosed buildings, the distribution of larger particles is not only dominated by gravity, but also by the convective transportation. Thus, even for the same wind direction and speed, the air quality may differ largely in the residential zones of different buildings. Wind direction has more significant impact on the particle concentration in the inner zones of unenclosed buildings than that in the courtyard. When the wind speed increased, the larger particle concentration reduces significantly, while the fine particle concentration has small increase in the courtyard. Thus, the courtyard has better performance for resisting particle entering under higher wind speed. Although the particle average concentration decreases when the wind speed increased, there are high pollutant concentration regions in the zone of unenclosed buildings.In conclusion, considering the long axis of building and prevailing wind direction incline to one another at the angle in the architecture planning (such as 45°), the courtyard can be used to create good air quality in the heavily particle polluted area. Specially, in the areas with high wind speed, the effect of cleanliness in courtyard may be more significant.