Numerical Simulation Of Wind And The Motor Mobile CO Pollutant Concentration Fields Inside Street Canyon

These years the number of the vehicles of the big cities in China is increasing with the high speed of 17%. It brings prosperity to the economy, but it also contributes much to the air pollution in big cities. According to the results of much research, vehicular exhaust is the main source of the air pollution in big cities and it directly leads to the deterioration of air quality in streets.It’s a complicated process for the vehicular exhaust to disperse in street canyon. Many factors may affect this process such as the source intensity, meteorological factors and street geometry and so on. Typical street model is built in thesis as the objects of this study. Then the characteristics and the current situation of vehicle emission are explored. Emphasis is put on how wind velocity、wind direction and street layout affect the dispersion process of the vehicular co pollutants in streets.The diffusive characteristics of vehicle emission pollutant and the wind field characteristics in urban street canyons depend on street canyon ration of height to width,A and the symmetry of building heightln this article ,a numerical model was used to study the relationship between street canyon characteristics and diffusive and wind characteristics.By using of Fluent CFD software.a 3-d two intersection model of three streets is set.The wind velocity distribution and CO concentration distribution near the intersection are simulated under 2 wind direction and 2 wind velocity conditions. The result of the modeling shows that the layout of the structures、the wind direction and the wind velocity can jointly affect the distribution of the wind velocity and the CO concentration. The stable vortexes from strong to weak strength are formed within the urban street canyon. The diffusive levels of the pollutant from urban street canyons are the street canyons in which the building in windward are highter than that of in leeward. The study of this thesis also shows that the modeling result of Fluent is reasonable and the application prospect of Fluent on atmospheric environment issues in urban streets is good.