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.

通过大涡模拟（LES）已经广泛研究了城市街道峡谷中的污染物扩散。LES的许多研究都集中在垂直于街道轴线的风向下的普通街道峡谷上。准确的LES模拟需要足够大的畴尺寸，以最大程度地减小畴面上人工边界条件对结果的影响。与RANS模拟相反，缺少关于街道峡谷中风流和污染物扩散的LES模拟的适当域大小的准则。本研究系统地研究了域宽度，域高度以及上游和下游域长度对具有跨展度周期性边界条件的普通2.5D街道峡谷内的风流和污染物扩散的影响。经过验证研究后，针对不同的域大小执行16次LES仿真。结果表明，对域宽度的最低要求是2.5H，其中H是街道峡谷的屋顶高度。对于磁畴高度，建议分别设置上游磁畴长度和下游磁畴长度7.5H，5H和10H。这些准则应有助于减少这种类型的仿真的计算成本，而不会显着影响精度。