On the Correlation of Air and Pollutant Exchange for Non-uniform Street Canyons

摘要

Air flow and pollutant dispersion in idealized non-uniform street canyons, composed of separated stepup and stepdown notches and a uniform notch in the middle, are investigated with Large-eddy Simulations (LES). Pollutant exchange rate is calculated at the roof level of the low buildings. Large scale vertical air movements are found in non-uniform street canyons, resulting of the increase of average velocity influence on pollutant exchange rate and the enhancement of pollutant escaping efficiency from the canyon to the aloft air. Sensitive analysis of average pollutant concentration at the pedestrian level to the height differences of buildings in the stepup and/or stepdown notches is conducted. Results show that even if only one floor of the buildings on the opposite sides of the canyon of the height difference, but also can cause differences in the average concentration at the pedestrian level of 20% compared to the uniform case.