CFD modelling of traffic-related air pollutants around an urban street-canyon in Suzhou

Abstract

The wind flow field around urban street-building configurations has an important influence on the microscale pollutant dispersion from road traffic, affecting overall dilution and creating localized spatial variations of pollutant concentration. It is important to understand these small-scale effects not only for assessing personal exposure to pollutants in the vicinity of roads, but also because air quality in a city as a whole is assessed on the basis of data from a few urban monitoring sites. This paper reports some outcomes of a study aimed at exploring the transfer and diffusion characteristics of vehicular exhaust emissions and the constraints associated with significant monitoring locations such as street canyons, courtyards and enclosed spaces, and the conditions propitious to pollutant diffusion and air dispersion in urban areas. The wind field around a street-canyon in the city of Suzhou (China) has been modelled by using the Computational Fluid Dynamic technique. The results have been analysed to better understand the values of gaseous pollutants, meteorological parameters and traffic flows measured by means of automatic analyzers along the same street-canyon at two different heights. It has been found that the model correctly describes the vortex recirculation pattern around the building geometry studied and it is very useful in assessing the micro-scale pollution trends.

Considerations for evaluating green infrastructure impacts in microscale and macroscale air pollution dispersion models

“…Most CFD models solve the governing nonlinear Navier Stokes equations, which are conservation of mass, momentum and energy, along with transport and/or any other user specific equations, with the help of any conventional methods such as the Finite Volume Method, Finite Element Method, Finite Difference Method and Spectral Methods. Many CFD models (Amorim et al, 2013;Baik et al, 2009;Costabile et al, 2006;Jeanjean et al, 2017Jeanjean et al, , 2015Kwak et al, 2018;Marciotto et al, 2010;Sanchez et al, 2016) have also been developed by researchers to simulate complex wind flows and pollutant transfer problems at different scales. Although CFD modelling has the capacity to deal with complex geometries, wind-induced turbulence and air pollutant transformations in simulating air pollutant concentrations (Amorim et al, 2013;Costabile et al, 2006;Jeanjean et al, 2015;Kwak et al, 2018;Lateb et al, 2016;Sanchez et al, 2016), they still require more validation to simulate the effects of modelled geometries on wind velocity and air pollutant concentration predictions in urban settings (Huang et al, 2009;Sini et al, 1996).…”

Spatial Distribution of Traffic Air Pollution and Evaluation of Transport Vehicle Emission Dispersion in Ambient Air in Urban Areas

“…No related published works have been carried out in the Chinese city of Suzhou, a medium-size municipality bordering the metropolitan area of Shanghai, in the middle of Yangtze River Delta, south of Jiangsu Province. This paper reports the preliminary outcomes of a bigger study aimed at assessing the representativeness of air quality data generated from the monitoring network of Suzhou city (12) . The focus of this study is addressed to explore the transfer and diffusion characteristics of vehicular exhaust emissions and the constraints associated with significant monitoring locations such as street canyons, courtyards and enclosed spaces, and the conditions propitious to pollutant diffusion and air dispersion in urban areas.…”