Numerical Study on the Impact of Ground Heating and
Ambient Wind Speed on Flow Fields in Street Canyons |
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Authors: | LI Lei YANG Lin ZHANG Li-Jie and JIANG Yin |
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Institution: | Shenzhen National Climate Observatory, Meteorological Bureau of Shenzhen Municipality, Shenzhen 518040;Shenzhen Meteorological Service Center, Meteorological Bureau of Shenzhen
Municipality, Shenzhen 518040;Shenzhen National Climate Observatory, Meteorological Bureau of Shenzhen Municipality, Shenzhen 518040;Shenzhen National Climate Observatory, Meteorological Bureau of Shenzhen Municipality, Shenzhen 518040 |
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Abstract: | The impact of ground heating on flow fields in street canyons under
different ambient wind speed conditions was studied based on numerical
methods. A series of numerical tests were performed, and three factors
including height-to-width (H/W) ratio, ambient wind speed and ground heating
intensity were taken into account. Three types of street canyon with H/W
ratios of 0.5, 1.0 and 2.0, respectively, were used in the simulation and
seven speed values ranging from 0.0 to 3.0 m s-1 were set for the
ambient wind speed. The ground heating intensity, which was defined as the
difference between the ground temperature and air temperature, ranged from
10 to 40 K with an increase of 10 K in the tests. The results showed that
under calm conditions, ground heating could induce circulation with a wind
speed of around 1.0 m s-1, which is enough to disperse pollutants in a
street canyon. It was also found that an ambient wind speed threshold may
exist for street canyons with a fixed H/W ratio. When ambient wind speed was
lower than the threshold identified in this study, the impact of the thermal
effect on the flow field was obvious, and there existed a multi-vortex flow
pattern in the street canyon. When the ambient wind speed was higher than
the threshold, the circulation pattern was basically determined by dynamic
effects. The tests on the impact of heating intensity showed that a higher
ground heating intensity could strengthen the vortical flow within the
street canyon, which would help improve pollutant diffusion capability in
street canyons. |
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Keywords: | street canyon thermal effect ambient wind ground
heating intensity computational fluid dynamics (CFD) |
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