Impact Factors on Airflow and Pollutant Dispersion in Urban Street Canyons and Comprehensive Simulations: a Review
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AIR POLLUTION (H ZHANG AND Y SUN, SECTION EDITORS)
Impact Factors on Airflow and Pollutant Dispersion in Urban Street Canyons and Comprehensive Simulations: a Review Yunwei Zhang 1 & Zhaolin Gu 1 & Chuck Wah Yu 1 Accepted: 18 October 2020 # Springer Nature Switzerland AG 2020
Abstract Purpose of Review The air quality management within urban street canyons can be improved by enhancing ventilation for dispersion of pollutants. The purpose of this review is to summarize effects of various impact factors on airflow and pollutant dispersion in urban street canyons. The relative intensity of different influence factors is reviewed, which should provide a useful comprehensive guide for modelling of these effects for urban developments. Recent Findings All reviewed numerical simulations, wind tunnel and outdoor scaled model experiments show that the various building heights and incoming airflow conditions could produce a clear influence on airflow and pollutant dispersion in urban street canyon. Outdoor scaled experiments have provided complex turbulent data and illustrated the complexity of airflow within urban street canyons, which would require comprehensive simulations to investigate the microclimate within these urban street canyons. Summary Impacts of thermal and/or wall heating conditions have been fully studied, while the impact of inflow variation, building height difference, model scale and the coupling effect of different factors are current hot topics for research. Building height difference and time-varying inflow conditions are factors of most significant influence, while tree planting, vehicleinduced turbulence, thermal and/or wall heat conditions have a relatively weak influence. Keywords Street canyon . Pollutant dispersion . Numerical simulation . Wind environment . Urban development . Impact factors
Introduction The rapid economic growth and urbanization, air pollution in urban areas have been causing serious harm in the last four decades to the urban environments and life quality and wellbeing of urban residents both physically and psychologically [1–3]. Pollutants of vehicle exhaust and the dispersion of pollutants in urban street canyons have been frequently investigated, showing reasonable urban and building designs could improve air ventilation under urban canopy layer and thus mitigate the intensities of air pollution and urban heat island (UHI) [4, 5••, 6–8].
This article is part of the Topical Collection on Air Pollution * Zhaolin Gu [email protected] 1
School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an, People’s Republic of China
In situ measurement, numerical simulation, wind tunnel simulation and outdoor downscale model experiment are methods usually used to study the airflow and pollutant dispersion characteristics within urban street canyons. Progress about the methods, especially about the numerical simulation method, has been reviewed in several literatures [9•, 10–14]. In numerical simulation, the Large Eddy Simulation (LES) method was found to b
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