Near-field pollutant dispersion in the built environment by CFD and wind tunnel simulations

Buildings are always found to be in the vicinity of other buildings, especially in urban areas. This causes effluents released from stacks located on one of the buildings to re-enter the same or an adjacent building, generating potential health problems to the occupants of the building. Earlier, Computational Fluid Dynamics (CFD) has been used in simulating pollutant transport for isolated buildings, with only few studies examining the effects of adjacent buildings. In this paper three cases that include an isolated low-rise building (source), a taller building placed upwind of the source and a case with taller buildings placed upwind and downwind of the source were considered. CFD simulations using the Realizable k–ε model for different turbulent Schmidt numbers (Sct) and wind tunnel experiments were performed for these cases. ASHRAE, 2007 was also used to assess plume dispersion for the isolated building. It was found that a strong dependence of Sct on CFD simulations of pollutant transport exists for the isolated building configuration. However, variations of Sct have less impact on assessing pollutant dispersion in the presence of adjacent buildings. The ASHRAE, 2007 model predicted very low dilutions for the isolated building, making it necessary to re-visit its formulations.