Turbulence and Pollutant Statistics around a High-Rise Building with and without Overhangs

Wind flow around an isolated building is highly turbulent. Facade appurtenances can further increase the complexity of the flow, which strongly affects the gas dispersion around the building. This study investigated the turbulence and pollutant statistics around a high-rise building with large-eddy simulations and determined the influence of overhangs on the local wind flow and dispersion. Large-scale periodic vortex motion was detected. The results indicated that both the oncoming flow and the flow around the building followed a standard Gaussian distribution, whereas the occurrence frequencies of pollutant concentrations were far from Gaussian for pollutants discharged from both the rooftop and the ground behind the building. Near the pollutant sources, the positive concentration fluctuations occurred more frequently; occasionally, positive and negative fluctuations occurred equally. For the majority of areas far from the source, negative fluctuations were more common, but the maximum positive fluctuations were much larger. Overhangs changed the local flow structures near the building facade. Both the maximum concentration fluctuation and the maximum occurrence frequency decreased in the region between overhangs because turbulence was restricted.