Wind Tunnel Simulation Of Near-surface Flow Field And Pollutant Dispersion In Main Urban Area Of Mengzi

The coordinated development of human and nature is the goal pursued by the city's sustainabledevelopment.With the rapid development of the economic society and the intensification of the urbanization level,the structure and function of the city have been changed greatly.The pollution problems of the urban area are also followed,then more and more people have pay attention to the air quality of urban environment.Mengzi belongs to the mountainous city of Yun-Gui Plateau,It's complex topography,low atmospheric pressure and abundant underlying surface conditions have caused great problems to the study of urban air pollution.Therefore,the environmental wind tunnel is used to study the near-ground flow field and the diffusion of pollutants in mountainous cities of the plateau,obtain the wind profile index and the atmospheric diffusion parameters,so as to predict the air pollution accurately,and then lay the foundation for the corresponding control measures.This paper taking the plateau mountain city?Mengzi,Yunnan province?as the research object,with the help of the Google earth,Global Mapper,Baidu map and other software,combined with the on-the-spot investigation,we make a terrain model of Mengzi city with the scale of 1:3000.And then analyse the near ground meteorological data and the sounding data to get the wind profile exponent of the Mengzi Meteorological Station.The wind tunnel flow field was adjusted according to the wind profile exponent.The flow field is similar through the combination of wedge and rough elements and wind barriers.Next,the wind tunnel tracer diffusion experiment was carried out,C₂H₄ was used as the tracer.Before the experiment,the standard curve of ethylene was measured.In combination with the C₂H₄standard curve,the concentration values of each measuring point can be obtained under the laboratory simulation condition.Combined with the dilution ratio of tracer gas,the concentration values of each measuring point can be obtained.and finally we can obtain the concentration distribution of the pollutants from the high elevation point source.Finally,this study calculated the horizontal diffusion equation and the vertical diffusion equation in Mengzi.The results show that the complexity of topography increases the intensity of turbulent flow in the near-earth layer,which has a great influence on the diffusion of pollutants,resulting in the increase of diffusion parameters.In addition,due to the inhomogeneity of spatial distribution,The normal distribution form of plume will be destroyed,which will affect the running track of pollutant smoke flow.