A photochemistry coupled computational fluid dynamics （CFD） based numerical model has been developed to model the reactive pollutant dispersion within urban street canyons, particularly integrating the interrelation...A photochemistry coupled computational fluid dynamics （CFD） based numerical model has been developed to model the reactive pollutant dispersion within urban street canyons, particularly integrating the interrelationship among diurnal heating scenario （solar radiation affections in nighttime, daytime, and sun-rise/set）, wind speed, building aspect ratio （building-height-to-street-width）, and dispersion of reactive gases, specifically nitric oxide （NO）, nitrogen dioxide （NO2） and ozone （O3） such that a higher standard of air quality in metropolitan cities can be achieved. Validation has been done with both experimental and numerical results on flow and temperature fields in a street canyon with bottom heating, which justifies the accuracy of the current model. The model was applied to idealized street canyons of different aspect ratios from 0.5 to 8 with two different ambient wind speeds under different diurnal heating scenarios to estimate the influences of different aforementioned parameters on the chemical evolution of NO, NO2 and 03. Detailed analyses of vertical profiles of pollutant concentrations showed that different diurnal heating scenarios could substantially affect the reactive gases exchange between the street canyon and air aloft, followed by respective dispersion and reaction. Higher building aspect ratio and stronger ambient wind speed were revealed to be, in general, responsible for enhanced entrainment of 03 concentrations into the street canyons along windward walls under all diurnal heating scenarios. Comparatively, particular attention can be paid on the windward wall heating and nighttime uniform surface heating scenarios.展开更多
基金supported by the ICEE of the University of Hong Kong and the Hong Kong Research Grant Council(Project HKU7146/06E)
文摘A photochemistry coupled computational fluid dynamics （CFD） based numerical model has been developed to model the reactive pollutant dispersion within urban street canyons, particularly integrating the interrelationship among diurnal heating scenario （solar radiation affections in nighttime, daytime, and sun-rise/set）, wind speed, building aspect ratio （building-height-to-street-width）, and dispersion of reactive gases, specifically nitric oxide （NO）, nitrogen dioxide （NO2） and ozone （O3） such that a higher standard of air quality in metropolitan cities can be achieved. Validation has been done with both experimental and numerical results on flow and temperature fields in a street canyon with bottom heating, which justifies the accuracy of the current model. The model was applied to idealized street canyons of different aspect ratios from 0.5 to 8 with two different ambient wind speeds under different diurnal heating scenarios to estimate the influences of different aforementioned parameters on the chemical evolution of NO, NO2 and 03. Detailed analyses of vertical profiles of pollutant concentrations showed that different diurnal heating scenarios could substantially affect the reactive gases exchange between the street canyon and air aloft, followed by respective dispersion and reaction. Higher building aspect ratio and stronger ambient wind speed were revealed to be, in general, responsible for enhanced entrainment of 03 concentrations into the street canyons along windward walls under all diurnal heating scenarios. Comparatively, particular attention can be paid on the windward wall heating and nighttime uniform surface heating scenarios.
