Experimental and numerical study of pollutant dispersion from traffic sources in a real urban neighbourhood

The present study aims to assess the impact of urban morphology and vegetative elements on the dispersion of pollutants emitted at ground level from traffic source. A neighbourhood in the historical city centre of Bologna (Italy) is selected as a case study: it is characterised by the presence of heavily trafficked roads, high trees and green areas. Airflow dynamics and pollutant concentration are reproduced and analysed by, both, laboratory experiments and high-resolved numerical simulations. Reynolds-Averaged Navier–Stokes (RANS) simulations are first validated against the experiments, then utilised to investigate the dispersion of pollutants in the city neighbourhood. Subsequently, full scale meteorological variables are used to inform the numerical simulation, through a downscaling procedure, to better reproduce and study the pollutant dispersion under a realistic atmospheric condition. The study enables a comparative analysis based on both experimental and numerical investigations, applied to a real urban geometry.