Experimental and numerical simulations of air quality in an urban canopy: Effects of roof shapes and atmospheric stability

The roof shapes of buildings and atmospheric stability play vital roles in dispersing and transporting pollutants in urban canopies. This study investigated the influence of roof shapes and atmospheric stability through experimental and numerical simulations. Wind flow and gas diffusion simulations were conducted around buildings in urban canopies using wind tunnel experiments and computational fluid dynamic models based on Reynolds-averaged Navier–Stokes models. Four building roof shapes and three atmospheric stability conditions were used in this study. The results of the experiment and numerical simulations were validated using quantitative computational models based on the validation metrics. The numerical simulation results corresponded with the experimental results for the flow and dispersion. The simulation results showed that the flow velocity of the slanted roof was higher than that of the other roof shapes. The pollutants accumulated near the slanted and pitched roofs' leeward side were higher than those in the flat and hip-shaped roofs. Pollutants in the building increased under stable atmospheric conditions and decreased under unstable atmospheric conditions.