Prediction and field observation for pollutant dispersion from vehicular exhaust plume in real atmospheric environment

A wind direction frequency weighted (WDFW) method based upon the atmosphere wind direction frequency characteristics, combining with solving the 3D Navier-Stokes equations, the mass and heat transfer equations as well as the standard k-ε turbulence models was proposed to model the local airflow and the dispersion of vehicular exhausted plume under real atmospheric conditions. The numerical results were compared and validated with the measured concentration and a good agreement was achieved. It is shown that the pollutant concentration is decreased rapidly with the distance from the tailpipe in a range of 1-4 m behind the tailpipe and the dispersion characteristics are mainly controlled by the exhaust flow rate and plume concentration, whilst those in a far region from the tailpipe exit are influenced by the ambient air and local weather conditions. However, the concentration still has high level at a height close to the breathing region along the tailpipe axis.