Modeling traffic pollutants in a street canyon by CFD: Idealized line sources versus multiple realistic car sources

P Qin; A Ricci; B Blocken

doi:10.1016/j.scitotenv.2024.177099

Modeling traffic pollutants in a street canyon by CFD: Idealized line sources versus multiple realistic car sources

Sci Total Environ. 2024 Dec 10:955:177099. doi: 10.1016/j.scitotenv.2024.177099. Epub 2024 Nov 3.

Authors

P Qin¹, A Ricci², B Blocken³

Affiliations

¹ Building Physics and Services, Department of the Built Environment, Eindhoven University of Technology, Eindhoven, the Netherlands. Electronic address: p.qin@tue.nl.
² Building Physics and Services, Department of the Built Environment, Eindhoven University of Technology, Eindhoven, the Netherlands; University School for Advanced Studies IUSS, Piazza della Vittoria 15, 27100 Pavia, Italy; Building Physics and Sustainable Design, Department of Civil Engineering, KU Leuven, Leuven, Belgium. Electronic address: a.ricci@tue.nl.
³ Institute of Mechanical, Process and Energy Engineering, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, Scotland, United Kingdom; Building Physics and Sustainable Design, Department of Civil Engineering, KU Leuven, Leuven, Belgium. Electronic address: b.blocken@hw.ac.uk.

PMID: 39461533
DOI: 10.1016/j.scitotenv.2024.177099

Abstract

Idealized sources are commonly used to reproduce the traffic emission in street canyons in experimental and numerical investigations. However, it remains unclear whether idealized sources can accurately reproduce the pollutant dispersion compared to more realistic sources. The goal of this paper is to investigate the impact of idealized and realistic sources on traffic-induced pollutant concentration in a street canyon by numerical simulation with Computational Fluid Dynamics (CFD). First, the scale-adaptive simulation (SAS) results of mean velocity and concentration are compared with wind-tunnel (WT) data for idealized line sources (ILS) and a satisfactory agreement is found between the SAS and WT results. Next, SAS are performed to investigate the impact on mean velocity and mean pollutant concentration of ILS versus multiple realistic car sources (MRCS) cases, designed to mimic a configuration of traffic jam-like conditions (i.e. rows of idling cars) in a street canyon. Different levels of geometrical simplifications of sources and total emission rates are considered. Although this research study focuses on these aforementioned specific set of conditions and conclusions relate solely to these circumstances, the SAS results show that the overall-averaged concentration associated with MRCS and the simplified source-geometry cases is about 1.18-6.22 times larger than that by ILS. Thus, ILS may be inadequate to reproduce the pollutant concentration in real scenarios. This study can contribute to enhancing the pollution prediction accuracy and reduce the potential risk of human exposure.

Keywords: CFD; Idealized/realistic source; Pollutant dispersion; Street canyon; Wind tunnel.