Computational fluid dynamics analysis of pollutant dispersion around a high-rise building: Impact of surrounding buildings

Abstract

Understanding the detailed mechanism of pollutant dispersion in urban areas is a critical aspect of air quality control in residential areas. In this study, wind tunnel measurements and high-resolution computational fluid dynamic (CFD) based on large eddy simulation (LES) were used for the detailed analysis of the pollutant dispersion around a high-rise building for an isolated case and also a case when the central high-rise building was surrounded by several low-rise buildings. The pollutant was released on the leeward façade of the high-rise building at the pedestrian height. It was shown that the presence of the surrounding buildings significantly alters the pollutant transfer mechanism around the high-rise building. In the surrounded case, the pollutant in the wake region shifted vertically toward the roof of the high-rise building. As a result, at a location of 2/3 of the high-rise building height, the mean concentration is five times larger than the isolated case, which means the residents on higher floors experience more pollution concentration in the case of the surrounded case even though they are located much higher than the canyon rooftop and the pollutant source. In both cases, the contribution of the turbulent diffusive flux in the streamwise direction is comparable with the mean convective flux while they have opposite directions. Detailed analyses of the pollutant mass transfer rate budget around different control volumes around the high-rise buildings highlighted the effect of the surrounding buildings. It is concluded that there is a risk of underestimating pollutant concentrations around a high-rise building, especially near the upper floors if the surrounding buildings are not properly considered.