Abstract
ABSTRACTMoving vehicles could have a considerable influence on air flow and turbulence within urban street canyons, especially the vehicle induced turbulence (VIT), which is an important consideration for pollutants’ dispersion and local air quality management. To simulate air flow in urban street canyons with moving vehicles, an Euler-Lagrangian method was further developed by this study. The method involved dynamically tracking each moving vehicle and determining the vehicle induced drag force on surrounding air. Simulations under different background wind velocities and vehicle speeds show that, moving vehicles could pose a strong effect on wind turbulence, but have a lesser effect on average wind field within a street canyon. The presence of VIT was mainly in the lower areas of a street canyon. The average standard deviation of velocity (σw0) in the lower areas is about 0.5 m s–1. In comparison with theoretical and experimental VIT models, VIT values produced by our simulations were higher than those obtained by experimental model, and were slightly lower than those produced by theoretical model. Instantaneous air flow fields within a street canyon were also investigated. Our results have indicated that the existence of local eddies could be a contribution factor to VIT.
Highlights
Exhaust fumes from motor vehicles are major sources of air pollution in urban environments (Perry and Gee, 1994; Cheng et al, 2012)
Moving vehicles could have a considerable influence on air flow and turbulence within urban street canyons, especially the vehicle induced turbulence (VIT), which is an important consideration for pollutants’ dispersion and local air quality management
Our results have indicated that the existence of local eddies could be a contribution factor to VIT
Summary
Exhaust fumes from motor vehicles are major sources of air pollution in urban environments (Perry and Gee, 1994; Cheng et al, 2012). Moving vehicles could induce air flow and turbulence to pose a significant influence on dispersion of pollutants in an urban street canyon, especially in lower areas of a street canyon (Qin et al, 1993) and/or under weak background wind conditions (Mazzeo and Venegas, 2005; Solazzo et al, 2007). Studying air flow and turbulence induced by moving vehicles is crucial for understanding pollutants’ dispersion characteristics in an urban street canyon (Zhang et al, 2012a). In-situ measurements, wind tunnel and numerical simulations have been conducted to determine air flow and pollutants’ dispersion characteristics in an urban street canyon (Zhang et al, 2013a).
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