Abstract
Large-eddy simulation was conducted to investigate the mechanism of pollutant removal from the there-dimensional street canyon. A tracer gas was released as a ground-level continuous gas line source at the center between three dimensional blocks. The results show that at least 75% of total emissions from the three-dimensional street canyon were attributable to turbulent motions. Pollutant removal by turbulent motions was related to the coherent structures of low-momentum fluid above the canyons. Though the coherent structure size of the low-momentum fluid differed, the positions of low-momentum fluid largely corresponded to instantaneous high concentrations of pollutant above the target canyon, irrespective of canyon geometry.
