Simulation Investigation of Nanoparticles’ Streamline and Distribution Pattern for a Moving Vehicle on a City Road

Abstract

In order to explore the nanoparticles’ movement and distribution pattern of a car emission, a 3-D CFD simulation code, based on Eulerian multiphase model, was developed and tested, the exhaust gas from the car is modeled as a mixture of air and seven kinds of particles: 10 nm, 70 nm, 100 nm, 300 nm, 500 nm, 1.0 μm and 2.5 μm. The model is validated before the typical city street simulation through a field experiment, and the simulation prediction is lower 4.1%, 5.1% and 8.2% than that the field test results for 300 nm, 500 nm and 1.0 μm particles. In city street case, when the car moving with a typical 50 km/h speed, the airflow at the bottom of the vehicle would lift the exhausting gas of the car and pressed down by the airflow from the top of vehicle thereafter. The particles are scattered behind the vehicle immediately, to occupy a larger space than the vehicle in width and height in a distance of a vehicle’s length behind, and concentrate behind the vehicle in a space no higher than the height of the vehicle. The distribution pattern of particles is symmetric with the axial of exhaust pipe in the horizontal plane and the higher the height, the smaller the distribution area, the diffusion range of the small particles is larger than the larger ones. The results of this paper could provide some ideas for the control of automobile exhausting gas pollution.