Large-eddy simulation of pollutant dispersion in generic urban street canyons: Guidelines for domain size.

Pollutant dispersion in urban street canyons has been widely investigated by large-eddy simulation (LES). Many LES studies focused on generic street canyons under a wind direction perpendicular to the street axis. Accurate LES simulations require a sufficiently large domain size to minimize the effects of the artificial boundary conditions at the domain faces on the results. As opposed to RANS simulations, there is a lack of guidelines for an appropriate domain size for LES simulations of wind flow and pollutant dispersion in street canyons. The present study systematically investigates the effect of the domain width, domain height and upstream and downstream domain lengths on the wind flow and pollutant dispersion within a generic 2.5D street canyon with spanwise periodic boundary conditions. Following a validation study, 16 LES simulations are performed for different domain sizes. The results show that the minimum requirement for the domain width is 2.5H, where H is the roof height of the street canyon. For the domain height, upstream domain length and downstream domain length, 7.5H, 5H and 10H are recommended, respectively. These guidelines should help to reduce the computational costs of this type of simulation without significantly compromising the accuracy. [Display omitted] • The accuracy of LES simulations requires a sufficient domain size. • Effect of the domain size on pollutant dispersion in 2.5D street canyon is studied. • The minimum requirement of domain height is estimated to be 7.5H. • The minimum requirement of domain width is estimated to be 2.5H. • The finding is helpful for saving numerical resources without compromising accuracy. [ABSTRACT FROM AUTHOR]