Numerical Modeling of the Dispersion of Vehicle Emissions in Street Canyons

Exhaust gas distribution in street canyons is one of the important research subjects in urban air quality studies. Vehicle emissions are an important group of pollutants in urban areas. In this study, the dispersion of exhaust emissions from vehicles in canyon type streets is modeled. The calculations were performed in two dimensions with the Computational Fluid Dynamics (CFD) method using the Fluent software. For the verification of the model results, wind tunnel test results obtained from the literature were used. For this purpose, the calculations were realized with the same boundary conditions as in the wind tunnel tests and the model results were compared with the test results. As in the experiments, a fully developed wind velocity profile in the perpendicular direction to the street-canyon was used, and the dispersion of a tracer gas injected into the canyon from a line source on the canyon base was determined. The distribution of pollutant gas concentration on the canyon walls obtained from the model calculations shows sufficient agreement with the experimental results. From the results can be seen that concentrations at the upwind building of the canyon are much higher than at the leeward building. In addition, concentrations at the upwind building decrease with height.