Lattice-Boltzmann Large-Eddy Simulation of pollutant dispersion in street canyons including tree planting effects

• Published in: Atmospheric environment (1994) 2018-12, Vol.195, p.89-103
• Main Authors: Merlier, Lucie, Jacob, Jérôme, Sagaut, Pierre
• Format: Article
• Language: English
• Subjects: 3D Street canyon; Chemical and Process Engineering; Computational fluid dynamics; Engineering Sciences; Large Eddy simulation; Lattice Boltzmann method; Tree crowns; Urban pollutant dispersion
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2018.09.040

This study assesses the performance of a large eddy simulation (LES) based on the lattice Boltzmann method (LBM) in predicting near field dispersion in street canyons with tree planting. Based on a benchmark test case benefiting from wind tunnel measurements (CODASC), this study qualitatively and quantitatively discusses the prediction of traffic-induced pollutant concentration with respect to several reference studies. It also analyses the physics of the flow and concentration fields. Although the problem might seem rather simple, the flow is highlighted to be strongly three dimensional and transient. These properties enhance pollutant dispersion in the empty street canyon but air flow velocity and turbulence intensity tend to decrease in tree crowns. This effect of trees increases both mean and peak concentration levels at pedestrian level, which may be problematic in cities with dense traffic. These results show that LBM-LES is particularly well suited to study dispersion problems towards the development of more breathable cities. •Pollutant dispersion in a street canyon using LES lattice Boltzmann method.•Rigorous model performance assessment with respect to wind tunnel measurements.•Analysis of the impact of trees on the fluctuating and time averaged velocity fields.•Analysis of the impact of trees on dynamic pollutant dispersion processes.•LBM-LES appears well suited for pollutant dispersion studies with tree plantings.