On the prediction of air and pollutant exchange rates in street canyons of different aspect ratios using large-eddy simulation

2005 ◽  
Author(s):  
C LIU ◽  
D LEUNG ◽  
M BARTH
Keyword(s):  
Large Eddy Simulation ◽  
Exchange Rates ◽  
Street Canyons ◽  
Eddy Simulation ◽  
Aspect Ratios ◽  
Large Eddy

Large-Eddy Simulation of Reactive Pollutant Dispersion Over Street Canyons of Different Aspect Ratios

2014 ◽  
Author(s):  
T. Z. Du ◽  
Chun-Ho Liu ◽  
Y. B. Zhao
Keyword(s):  
Aspect Ratio ◽  
Large Eddy Simulation ◽  
Chemical Reactions ◽  
Pollutant Dispersion ◽  
Pollutant Removal ◽  
Street Canyons ◽  
Eddy Simulation ◽  
Aspect Ratios ◽  
Large Eddy ◽  
Reactive Pollutant

In urban areas, pollutants are emitted from vehicles then disperse from the ground level to the downstream urban canopy layer (UCL) under the effect of the prevailing wind. For a hypothetical urban area in the form of idealized street canyons, the building-height-to-street-width (aspect) ratio (AR) changes the ground roughness which in turn leads to different turbulent airflow features. Turbulence is considered an important factor for the removal of reactive pollutants by means of dispersion/dilution and chemical reactions. Three values of aspect ratio, covering most flow scenarios of urban street canyons, are employed in this study. The pollutant dispersion and reaction are calculated using large-eddy simulation (LES) with chemical reactions. Turbulence timescale and reaction timescale at every single point of the UCL domain are calculated to examine the pollutant removal. The characteristic mechanism of reactive pollutant dispersion over street canyons will be reported in the conference.

scholarly journals Flow and Pollutant Transport in Urban Street Canyons of Different Aspect Ratios with Ground Heating: Large-Eddy Simulation

2011 ◽  
Vol 142 (2) ◽  
pp. 289-304 ◽  
Author(s):  
Xian-Xiang Li ◽  
Rex E. Britter ◽  
Leslie K. Norford ◽  
Tieh-Yong Koh ◽  
Dara Entekhabi
Keyword(s):  
Large Eddy Simulation ◽  
Pollutant Transport ◽  
Street Canyons ◽  
Urban Street ◽  
Eddy Simulation ◽  
Urban Street Canyons ◽  
Aspect Ratios ◽  
Large Eddy

Large-eddy Simulation of Plume Dispersion over Hypothetical Urban Areas

2020 ◽  
Author(s):  
Zhangquan Wu ◽  
Chun-Ho Liu
Keyword(s):  
Nitric Oxide ◽  
Air Quality ◽  
Large Eddy Simulation ◽  
Urban Areas ◽  
Turbulent Dispersion ◽  
Anthropogenic Sources ◽  
Plume Dispersion ◽  
Street Canyons ◽  
Eddy Simulation ◽  
Large Eddy

<p>More than 80% of people living in urban areas that exposed to air quality levels that exceed WHO guideline limits both indoors and outdoors. Road transport has been found to be one of major anthropogenic sources of aerosol particles and many gaseous pollutants in urban areas. Dispersion of pollutants emitted from vehicles over urban areas largely affects pedestrian-level air quality. A good understanding of pollutant transport, mixing process and removal mechanism is crucial to effectuate air quality management. In this study, turbulent dispersion of reactive pollutants in the atmospheric boundary layer (ABL) over hypothetical urban area in the form of an array of idealised street canyons is investigated using large-eddy simulation (LES). The irreversible ozone O3 titration oxidizes nitric oxide NO to nitrogen dioxide NO2, representing the typical anthropogenic air pollution chemistry. Nitric oxide (NO) is emitted from the ground level of the first street canyon into the urban ABL doped with ozone (O3). From the LES results, negative vertical NO flux is found at the roof level of the street canyons.  By looking into the different plume behavior and vertical flux between the inert pollutant and chemically reactive pollutant, a fundamental understanding of exchange processes of anthropogenic chemicals between an urban surface and the atmosphere is developed. </p>

scholarly journals Large-Eddy Simulation of Flow and Pollutant Transport in Urban Street Canyons with Ground Heating

2010 ◽  
Vol 137 (2) ◽  
pp. 187-204 ◽  
Author(s):  
Xian-Xiang Li ◽  
Rex E. Britter ◽  
Tieh Yong Koh ◽  
Leslie K. Norford ◽  
Chun-Ho Liu ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Pollutant Transport ◽  
Street Canyons ◽  
Urban Street ◽  
Eddy Simulation ◽  
Urban Street Canyons ◽  
Large Eddy
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