A Study of Downwash Effects on Flow and Dispersion Processes around Buildings in Tandem Arrangement

Air pollution is one of the world's most important problems. Our paper presents and discusses the relationship between a structure of a flow field among neighboring buildings immersed in a boundary layer, and characteristics of pollutant dispersion in that area. The flow and dispersion of gases emitted by a point source located in front of the buildings also were determined by numerical model with the use of a commercial CFD code (Ansys FLUENT). This paper presents the results of a complex research program aimed at understanding the character of the flow field around groups of buildings in urban areas and the unsteady phenomena resulting from the character of the wind or from the interference of the wake flow connected with the vortex-shedding process. The results showed that it is the factor-affecting process of the dispersion of pollutants in the built-up area that is more complex than the propagation of small parts explained on the basis of the processes of advection and turbulent diffusion.