STUDY OF LINE SOURCE CHARACTERISTICS FOR 2-D PHYSICAL MODELING OF POLLUTANT DISPERSION IN STREET CANYONS

The University of Hamburg initiated a wind tunnel study of car exhaust dispersion from street canyons in an urban environment to investigate how pollution dispersion is affected by street geometry. Particular e mphasis at the beginning of this work was put on the design of a line source to represent traffic exhaust. Pollution dispersion was studied in two dimensions (i.e., infinite-length streets were assumed). The ca se of an isolated street canyon in open country was examined first, Th e same street canyon geometry was subsequently studied in an urban env ironment, i.e., with additional canyons of similar geometry upstream a nd downstream of the test street. The dynamic and dispersion character istics of the flow in the two cases were quite different. In the canyo n amidst open country we observed better canyon ventilation than in th e urban roughness case.