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Open AccessArticle

Effects of Ground Heating on Ventilation and Pollutant Transport in Three-Dimensional Urban Street Canyons with Unit Aspect Ratio

1
Department of civil and environmental engineering, Shantou University, Shantou 515063, China
2
College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620, China
*
Author to whom correspondence should be addressed.
Atmosphere 2019, 10(5), 286; https://doi.org/10.3390/atmos10050286
Received: 23 April 2019 / Revised: 11 May 2019 / Accepted: 17 May 2019 / Published: 21 May 2019
A validated standard k-ε model was used to investigate the effects of ground heating on ventilation and pollutant transport in a three-dimensional (3D) street canyon. Air entered the street canyon from the upper regions of side surfaces and most areas of the top surface and left from the lower regions of side surfaces. Ground heating enhanced the mean flow, ventilation, and turbulence, and facilitated pollutant reduction inside street canyons. The transport patterns in a street canyon that included a pollutant source (PSC) and a target street canyon downstream (TSC) were different. The pollutant did not enter the PSC, and turbulent diffusion dominated pollutant outflow at all boundaries. The pollutant entered the TSC from most regions of the side surfaces and exited from lower regions of the side surfaces and the entire top surface. Air convection dominated pollutant transport at the side surfaces, and its contribution increased significantly with ground temperature; Furthermore, turbulent diffusion dominated pollutant outflow for the top surface, and its contribution increased slightly with ground heating. As revealed by an analysis of both the total pollutant flow rates and air flow rates, although air/pollutant exchange between the TSC and outer space occurred primarily through the side surfaces, the increase in air inflow from the top surface reduced the pollutant concentration inside the street canyon when the ground temperature increased. The top surface played a major role in improving air quality in a 3D environment with ground dispersion. This study supplied valuable suggestions for urban planning strategies. The analyzing method used in this research is helpful for the pollutant transport investigations in urban areas. View Full-Text
Keywords: street canyon; ground heating; ventilation; pollutant transport; computational fluid dynamics (CFD); Reynolds-Averaged Navier-Stokes (RANS) street canyon; ground heating; ventilation; pollutant transport; computational fluid dynamics (CFD); Reynolds-Averaged Navier-Stokes (RANS)
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Jiang, G.; Hu, T.; Yang, H. Effects of Ground Heating on Ventilation and Pollutant Transport in Three-Dimensional Urban Street Canyons with Unit Aspect Ratio. Atmosphere 2019, 10, 286.

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