Physical Simulation of Automobile Exhausts Dispersion at an Urban Intersection – Part I: Concentration Fields and Dispersion

The major sources responsible for deterioration of urban environments are automobiles. The case at urban intersection may become more critical due to variable modes of vehicular movement and their emissions, especially at low wind conditions. In this paper, the line source dispersion and concentration fields at an urban intersection under low wind conditions have been investigated and discussed. The atmospheric boundary layer (ABL) flow equivalent to urban terrain category, is reproduced using passive type of roughness generating devices with appropriate similarity criteria. The line source is simulated and tracer gas concentrations at various locations of the intersection are measured using online Flame Ionization Detector (FID) type of gas chromatograph. The experiments are carried out for 0 0 , 30 0 and 60 0 approaching wind directions. The experimental results show various critical locations, where pollutant concentrations become twice or even more. The approaching wind directions of 30 0 and 60 0 carry more dispersion of pollutants than 0 0 . However, the pollutants concentrations at inner corners of building blocks are more than at other locations.