Numerical Simulation Of Key Factors Of Atmospheric Pollutant Dispersion Over Comlex Underlying Surface

With the prosperity and development of society and economy,the scale of cities is expanding day by day,and the conditions of underlying surface are becoming more and more complicated.Haze,urban heat island phenomenon,traffic exhaust and factory emissions make pollutants gather more seriously in cities.Therefore,urban environmental quality has attracted more and more people's attention.Therefore,it is one of the urgent tasks for researchers to study the prediction and optimal control of air pollution and its effects.Air pollution control should not only strengthen management,but also combine scientific methods.Atmospheric transmission and diffusion is an extremely complex process,which is affected by many factors,especially the influence of complex underlying surface.In order to better simulate and reproduce the diffusion law of pollutants,this paper established relevant physical models of different underlying surfaces,and combined field experiments and CFD numerical simulation methods to explore the influence of different underlying surfaces on wind field and the diffusion of pollutants.The main research work can be divided into the following aspects:(1)At first,this paper establishes the common in the city of four different types of underlying surface(buildings,shrubs,trees,water),physical model,respectively set up no underlying surface conditions,shrubs in before and after the pollution sources,trees in pollution sources,water,in the before and after the pollution sources of 10 kinds of before and after contrast model,sets the vegetation canopy part to porous media and atmospheric pollutants identified as sulfur hexafluoride.The standard k-epsilon turbulence model and the components combined transport equation of the numerical simulation method,the comparison between different location on the same model and different models of the flow field distribution and diffusion of pollutants,get different underlying surface type affect the spread of atmospheric transmission law,and based on the simplified model of rule,for subsequent various underlying surface coupling of real model provides guidance and direction.(2)Combined with several modeling software,a real model which is basically consistent with the actual situation of a university is established,including several underlying surface types discussed above,and the trees are divided into medium trees and high trees.CFD software was used for numerical simulation of the complex underlying surface model,and the diffusion law of pollutants was analyzed as a whole.The pollutants mainly dispersed with the prevailing wind direction,and the vegetation could inhibit their diffusion to a certain extent.In order to find out the characteristics of pollutant diffusion and distribution in this area,the tracer experiment of sulfur hexafluoride was carried out in the campus.The measured data of wind speed and pollutant concentration were compared with the simulated data,and the accuracy of CFD method was verified.Through numerical simulation and field experiment on key factors of atmospheric pollutant diffusion over complex underlying surface,the large airflow field and pollutant diffusion law under dominant wind direction are summarized.The research results of this paper can provide an analytical reference for urban construction planning and the simulation of the diffusion of air pollutants in the campus,and to a certain extent,it can also provide feasible advice in the case of emergency.