Validation and Application of CFD Modeling for Predicting Traffic Induced Air Pollution in a Complex Urban Area

Traffic induced air pollution along roadside in large cities is still an environment challenge despite significant improvements in fuel and engine technology. This is because the vehicle emissions are trapped along the road due to the high-density use of space, such as high-rise buildings in urban areas and multi-layered roadways. In order to study the air pollution induced by vehicle transportation, comprehensive investigations have been launched, including field measurement and numerical predictions, over a complex urban area including multi-layered roadways and many buildings in Kawasaki city, Japan. This paper presents the three-dimensional Computational Fluid Dynamics (CFD) simulation of the wind environment and pollutants dispersion within the objective area covering a range of 1.5km×1.5km. Simulation was conducted under the same pollutant emission intensity and meteorological conditions as observed in the field measurement. The analysis of wind speed and pollutants was carried out at the pedestrian level (1.5 meters above ground level). Simulation results also illustrated which area would be subject to high concentrations due to air stagnation and pollutant accumulation. The prediction accuracy was examined by comparing the numerical results with the actual measurements. Furthermore, the urban thermal situation is thought to have a great influence on the air pollution. In this study, the influence of the atmospheric stability on the air pollution is analyzed using the validated CFD modeling.