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Title: Air ventilation impacts of the “wall effect” resulting from the alignment of high-rise buildings
Authors: Yim, Steve Hung-Lam
Fung, Jimmy Chi-Hung
Lau, Alexis Kai-Hon
Kot, See Chun
Keywords: Air ventilation
Wall effect
Retention time
Velocity ratio
Pollutant dispersion
Urban air quality
Issue Date: Oct-2009
Citation: Atmospheric environment, v. 43, iss. 32, p. 4982-4994
Abstract: The objective of this study is to investigate the air ventilation impacts of the so called “wall effect” caused by the alignment of high-rise buildings in complex building clusters. The research method employs the numerical algorithm of computational fluid dynamics (CFD) to simulate the steady-state wind field in a typical Hong Kong urban setting and investigate pollutant dispersion inside the street canyon utilizing a pollutant transport model. The validation study on our model settings was accomplished by comparing the simulation wind field around a single building block to wind tunnel data. The results revealed that our model simulation is fairly close to the wind tunnel measurements. In this paper, a typical dense building distribution in Hong Kong with 2 incident wind directions (0° and 22.5°) is studied. Two performance indicators are used to quantify the air ventilation impacts, namely the velocity ratio ( VRw ) and the retention time ( Tr ) of the dispersion of pollutants at the street level. We found that the velocity ratio at 2m above ground was reduced 40% and retention time of pollutants increased 80% inside the street canyon when high-rise buildings with 4 times height of the street canyon are aligned as a “wall” at the upstream. While this reduction of air ventilation was anticipated, the magnitude is significant and this result clearly has important implications for building and urban planning.
Rights: Atmospheric environment © copyright (2009) Elsevier. The Journal's web site is located at
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