Large-eddy simulation of pollutant dispersion in generic urban street canyons: Guidelines for domain size
Xing Hua Zheng, Hamid Montazeri, Bert J. E. Blocken · 2021 · 74 citationsRead the paper
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.
What the full text shows
Shown in the lab- Minimum recommended domain width to ensure similarity in mean velocity and concentration. — 2.5H (2.5D street canyon with spanwise periodic boundary conditions)
- Recommended domain height to minimize blockage effects (equivalent to 13.3% blockage ratio). — 7.5H (2.5D street canyon with spanwise periodic boundary conditions)
- Recommended minimum upstream domain length. — 5H (2.5D street canyon with spanwise periodic boundary conditions)
- Recommended minimum downstream domain length. — 10H (2.5D street canyon with spanwise periodic boundary conditions)
- Average absolute difference in mean velocity magnitude (U3D/Uref) when using a domain width of 2.5H compared to 7.5H. — 0.020 (2.5D street canyon center region)
- Average absolute difference in mean concentration (C+) when using a domain width of 2.5H compared to 7.5H. — 0.119 (2.5D street canyon center region)
- Setup
- Generic 2.5D street canyon with building height (H) of 12m and street width (W) of 12m (aspect ratio 1:1), using spanwise periodic boundary conditions.
- How
- The researchers performed 16 Large-Eddy Simulations (LES) using a test matrix to vary domain width, height, and upstream/downstream lengths. Results were validated against wind-tunnel data for mean vertical velocity and pollutant concentration.
- Limitations
- Limited to simple street canyons with an aspect ratio of 1:1. · Not applicable to cases with building facade geometrical details (e.g., balconies). · Not tested for multiple street canyons in sequence or with upstream obstacles.
Summarized by Gemma 4 from the open-access full text · 7 Oct 2026. Read it