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

Abstract

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.

Actuator line simulations of wind turbine wakes using the lattice Boltzmann method

“…To date, one of the few prominent applications in the wider field of atmospheric flows are wind comfort assessments and pollution dispersion in urban canopies (e.g. King et al, 2017;Ahmad et al, 2017;Jacob and Sagaut, 2018;Lenz et al, 2019;Merlier et al, 2018Merlier et al, , 2019. Other related applications are wind load assessments as presented by Andre et al (2015), Fragner and Deiterding (2016), or Mohebbi and Rezvani (2018).…”

Lattice Boltzmann Method-Based Simulations of Pollutant Dispersion and Urban Physics

“…Simulations were run on 240 cores for 25 s physical time, with the last 10 s being kept for postprocessing. Details can be found in Merlier et al's work [32]. Quantitative (Table 4) and qualitative (not shown) comparisons of experimental and numerical mean concentrations on the leeward and windward walls of the street canyon highlight a state of the art performance of the HRR-LB model as compared to other reference studies.…”

Urban Vegetation in Air Quality Management: A Review and Policy Framework

“…Computational fluid dynamics (CFD) simulations with established, previously validated models or models validated against data from previous studies or existing databases [9,77,79,[85][86][87][88][89][90][91] CFD simulations and on-site air quality measurements, or measurements of pollution deposition on plant samples using laboratory techniques or wind tunnel experiments [78,92,93] CFD simulations coupled with photochemical equations for NO X , and O 3 transport [94] Coupled CFD-Lagrangian stochastic model (CFD-LSM) simulations [95] Parallelized Large-Eddy Simulation Model (PALM) with embedded Lagrangian stochastic particle model (LPM) simulations [96] In the studies accounting for the aerodynamic effects, the local or neighbourhood scale was applied (see Table 4). At the local scale, street canyons were mainly investigated, using either idealised 2D [78,92] or 3D street canyon geometries [83,85,89,90,95] or more realistic street canyon models based on existing geometries [93]. Idealised urban blocks, consisting of an array of buildings with several street canyons [87,88,94], were also used as a computational domain.…”