Influences of Mutual-Building Heights on Aerosol Flow and Pollutants Dispersion in Urban Street Canyons under Haze-Fog Conditions

In the present paper, a two-phase simulation of atmospheric aerosol (air, pollution, fine particles of dust, and vehicles pollutants) is carried out to investigate the pollutants dispersion and heat transfer (conduction-convection-radiation) in urban street canyons under haze-fog conditions. Numerical calculations were considered for four time periods during the day, including: 10 am, 1 pm, 4 pm, and 8 pm on the first days of April, July, October, and January. For this purpose, Computational Fluid Dynamics (CFD) method and the simulation are used and dynamic characteristics of airflow and heat transfer have been obtained. The results show that the trend of the ground temperature variation in different months is the same and the maximum value of it has always occurred at 1 pm. In addition, in all the hours and months that examined in the present study, the natural convection for the fluid flow than the forced convection is insignificant, and the main of the fluid flow and pollutants is due to the wind velocity at the inlet boundary condition and the pollutants velocity. In cases with higher windward wall and small aspect ratio between buildings and street, the lowest pollutant concentration in passengerchr('39')s level is achieved.