Computational Model for Transient Pollutants Dispersion in City Intersection and Comparison with Measurements

Abstract

Many city intersections are often heavily polluted due to intensive traffic. Dispersion of pollutants originating from traffic is directly connected with the geometry of the urban area and traffic conditions. The urban area is mostly heavily built-up area and buildings and other obstacles that may significantly influence local concentrations. Moving vehicles enhance both microand large-scale mixing processes in their surroundings. Not taking into account traffic will lead to neglecting one of the most important phenomena that influences mixing processes in the proximity of traffic paths. The influence of traffic is increasingly important in situations of very low wind speed. In this study, the authors focus on transient pollutant dispersion due to traffic dynamics in an actual intersection equipped with traffic lights located in the center of the city of Brno. Inclusion of traffic dynamics leads to a better description of dispersion processes. Information about traffic situations were obtained from in-situ measurements. A model based on a Eulerian – Lagrangian approach to moving objects has been developed and integrated into a commercial CFD code StarCD. Results of CFD predictions of NOx concentrations are compared with measurements acquired from an automatic monitoring station located in the intersection.