Abstract

A detailed and comprehensive numerical study of wind-induced pollutant dispersion around buildings has been carried out. Research in this area was reviewed and analyzed. The results from various studies were compared. Based on the review and the comparison with various studies, a more effective methodology for the numerical evaluation of dispersion of pollutants around buildings has been proposed. Computed results of a two-layer approach show various degrees of improvement for the concentration field in the wake region and on the back wall of the building. Results from two-layer approach also show improvement on the building roof for along-wind direction. However, the two-layer approach does not seem to work well for roof concentration along the cross-wind direction; this is probably due to the drawback of the isotropic turbulence model used. The previous numerical studies on pollutant dispersion around rectangular buildings only investigated the concentration profiles for along-wind direction or vertical direction, and these were only for limited situations. A systematic examination of pollutant concentration in the wake of a rectangular building has been carried out for two different release sources. The concentration profiles have been investigated for along-wind, across-wind and vertical directions for various locations. The numerical simulation results have been compared with those from the experiments and from the Modified Gaussian Model. Results from numerical simulation generally agree well with those from the experiments. It was found that the numerical simulation predicts ground level pollutant concentrations better than the Modified Gaussian Model in the near building wake area. The influence of numerical errors on the computed results and the effects of thresholds in the demoralization and convergence process have been investigated for the first time in the area of numerical simulation of pollutant dispersion around buildings