Neighborhood scale traffic pollutant dispersion subject to different wind-buoyancy ratios: A LES case study in Singapore

Shuo-Jun Mei; Yongling Zhao; Tanya TalwarJan CarmelietChao Yuan

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Neighborhood scale traffic pollutant dispersion subject to different wind-buoyancy ratios: A LES case study in Singapore

机译：Neighborhood scale traffic pollutant dispersion subject to different wind-buoyancy ratios: A LES case study in Singapore

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This study explores the buoyancy effect on traffic pollutant dispersion at neighborhood scale, in which a wide range of wind-buoyancy ratios is examined. Pollutant dispersion is solved using a Large Eddy Simulation (LES) turbulence model, where realistic urban morphology and historical traffic pollutant emission data are adopted. For no incoming wind condition, thermal plumes develop and entrain horizontal flow near ground level. This neighborhood scale buoyancy-driven flow leads to air pollutant dispersion, which is as strong as wind-driven dispersion in the target area. As a result, urban air pollutant accumulation is limited due to buoyancy, regardless of ambient wind conditions. A light incoming wind can flush upward thermal plumes downstream when the Richardson number (Ri) reaches 25.5. The interplay of the approaching wind and upward plumes from urban surfaces leads to an oscillatory flow, which intensifies local turbulence and enhances the pollutant removal rate. At the pedestrian level, the neighborhood scale average NO_2 concentration due to the traffic emission ranges from 4.1 μg/m~3 to 4.8 μg/m~3. The minimum value is found for a weak incoming wind condition, (coupling with buoyancy, Ri = 25.5) and the maximum value is observed for the no incoming wind condition (Ri = ∞). The modelling result analysis clarifies how buoyancy-related dispersion, emission location, surrounding urban density, and incoming wind affect local pollutant concentrations. The research outputs highlight the importance of these coupling effects in the air pollutant dispersion evaluation in real urban areas.

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来源
《Building and environment》 |2023年第1期|109831.1-109831.16|共16页
作者
Shuo-Jun Mei; Yongling Zhao; Tanya TalwarJan CarmelietChao Yuan;
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作者单位

Department of Architecture, National University of Singapore, Singapore;

Department of Mechanical and Process Engineering, ETH Zuerich, Switzerland;

Department of Architecture, National University of Singapore, Singapore, School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai, China;

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正文语种英语
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关键词
Buoyancy effect; Extreme low wind; Large-eddy simulation; Neighborhood scale; Traffic pollutant dispersion;

Neighborhood scale traffic pollutant dispersion subject to different wind-buoyancy ratios: A LES case study in Singapore

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