Numerical simulation of pollutant dispersion in an urban street canyon - effects of elevated metro rail track

Urban air pollution is one of the unsettled issues in urban development and planning process. Urban street canyons are one of the main focused areas of investigation due to the heavy emission of the pollutants from vehicles. In the present study, the effects of elevated metro rail track (EMRT) on pollutant dispersion phenomena have been studied using computational fluid dynamics (CFD) technique. As a practical application of a CFD model, k-ε turbulence model was applied for airflow modelling. Species transport model was applied for pollutant dispersion modelling. Geometrical configuration of urban street canyon of aspect ratio 'one', with elevated metro rail track, has been considered. Numerical simulations were carried out for perpendicular wind flow. Pollutant concentrations, at various locations of the street canyon, were largely affected by the introduction of elevated metro rail track. These results were compared with the street canyon without elevated metro rail track. It has been observed that the pollutant concentration increased at lower region and decreased at the upper region of the street canyon. Variations were not uniformly distributed in street canyon volume. Contours and pollutant concentrations have been compared and discussed for different sampled locations in the street canyon.