Study On The Space Optimization Of Beijing Jianwai Street Based On The Theory Of Automobile Exhaust Pollution In Urban Street Canyons

With the rapid process of urbanization, China’s environmental pollution problems have become more and more outstanding. In large cities, high-rise buildings on both sides of the motor vehicle road and narrow city roads form a "street canyons" spatial structure. In urban street canyons, because traffic is heavy and centralized, motor vehicle exhaust pollutants released to more than the average urban space, combined with the surrounding space more closed, resulting in high concentrations of air pollutants in street canyons, seriously endangering the health of pedestrians around the road. Therefore, the study of urban street canyons distribution and diffusion of pollutants in the law has positive significance for improving urban air quality and optimizing the urban spatial structure.This paper summarizes the mechanism of pollutant diffusion in urban street canyons, field research and measurement Beijing Jianguomenwai Avenue Street PM2.5 concentrations valley daily changes and vertical changes.On this basis, the application of CFD software, combined with the climate in Beijing, Jianguomenwai Avenue in Beijing urban street canyons numerical simulation analysis to identify the relationship between the distribution of contaminants and street canyons spatial structure. Simulation results show that:the highest regional concentration of pollutants focus on the height of 1 Om below, as the height increases the concentration of pollutants decreases; airflow parallel to the street canyon has no effect to air purification, sculptors will introduce contaminants into the valley Street; concentration of pollutants around the leeward side of the Valley Street building is much higher than the concentration of pollutants around the windward side of the building; upwind building on the street canyon should not be arrangement too high, excessive building height will become cleaning barrier to flow into the Valley Street, and it is harmful to Street valley diffusion of pollutants; open Spac disposed around the upwidn buildings in the street will beneficial to Street valley diffusion of pollutants.hollow portion in the back to shape building is easy to accumulate large quantities of pollutants, and therefore should not be arranged on the wind Street Valley.Finally, this paper summarizes the mechanism of distribution and diffusion of pollutants in urban street canyons and analyzed to build the basic law of the street outside the valley PM2.5 Street diffusion based on the results of the results of field measurements and numerical simulations with a view to the future of urban planning-related It provides a design strategy.