Air,Heat And Pollutant Transports And Their Dynamical Characteristiscs Of The Urban City

With the urbanization developing increasingly,the urban population increasing constantly,the urban traffic and industrial waste gas discharge amount increasing and the urban air environment worsening constantly,the microclimate air environment around the urban architecture affects the resident breathe health,which fully understands that the microclimate air and heat and pollutant transportation mechanism around the urban architectures are beneficial to find the effective means or methods of improving the breathe environment of urban residents and guaranteeing the breathe health of urban residents.Based on it,the passage carries out the relevant basic scientific research work from the secondary gaseous pollutant diffusion mechanism,the inland urban lake and urban heat island circulation coupling features generated by photo chemical reaction,which is caused by the air environment caloric transportation process structure of the urban internal block and the industrial waste gas emission of urban traffic.Firstly,considering that it is particularly evident to represent the urban environment problems in the block with many people activities because it is the carrier of transport and migration between heat and pollutant in the cities,starting from the basic block unit in the city,the paper mainly conducts numerical studies of transport and migration characteristics of fluid flow,heat and pollutants in the urban block canyon based on the CFD method.And the numerical model mainly selects a block canyon with a typical aspect ratio of W/H=1.0,which represents the comprehensive shape of most modern urban centers.During the numerical simulation coupling process of transport migration between heat and pollutants,the paper first introduces isopleth of the flow function,the thermal function and the mass function to characterize the heat transport process in the urban block canyon,and further adopts the ACR?air change rate?,HRR(?heat removal rate?and PRR?pollutant removal rate?parameters to determine the ventilation air flowing efficiency and thermal transport characteristics in the block canyon,thus helping learn the interaction between airflow and thermal buoyancy lift in the windward and leeward,and better mastering the heat transport process in the canyon.Then,considering that most of the gaseous pollutants discharged in the urban traffic are chemically reactive,in order to explore the migration and diffusion law of gaseous pollutants under photochemical reactions,this paper mainly carries out numerical studies of the diffusion of reactive pollutants in the canyon by using the representative NO-NO₂-O₃ photochemical reaction coupling CFD model.In addition,the paper also uses the RNG k-?turbulence model coupling to first study the migration and diffusion law of gaseous pollutants after photochemical reaction under the conditions of different vehicle exhaust emissions in the block,and based on the more realistic atmospheric environment,further considers the impact of traffic exhaust source of NOx on the photochemical reaction and the diffusion and migration of gaseous pollutants in the urban block canyon.The urban underlying structure always plays an important role in the urban air environment though the rapid development of urbanization has gradually led to the urban land use in industry and construction areas,as well as a sharp decrease in urban green coverage and water area,therefore,the paper changes the previous research target and focuses on the urban unit instead of the basic block unit.On this basis,in order to explore the influence of the urban underlying surface structure,especially the typical inland lake urban water-body,on the urban air thermal environment,starting from the basic observation of experiments,the paper explores the influence of the lake water structure on the urban environment,and further uses numerical simulation to develop the urban heat island and lake wind circulation model,in order to master the other laws.And the simulation study shows that the displacement of urban heat island plume would decrease along with the distance increase of lake and urban center when the lake area of typical inland lake is unchanged.However,the displacement of urban heat island plumes can decreases along with the increase of lake area in the case of changing distances to urban and lake center,which can be seen that the underlying surface structure of the lake water body has a significant effect on the urban air environment.And this paper first starts from the research of the thermal transport mechanism of the urban block environment,then the transport law of pollutants under the more realistic photochemical pollution in the urban block,and finally explores the impact of typical lake water body structure of the inland city in the urban underlying structure on the air thermal environment.In order to solve the problems generated in the urban environment,the paper believes that it is not only necessary to study the heat transport process in the basic urban block canyon and fully grasp the flow heat transfer mechanism,but to better master the diffusion process of the pollutants in the block environment under more realistic photochemical pollution.In this way,it can realize better control and prevent the spread of pollutants staring from the basic urban canyon,in order to further provide better conditions for the heat transport.What's more,based on China's basic national conditions and realities,and the lake water body structure of most typical inland lakes in our country,it is necessary to use the advantages of the urban underlying surface structure to create a more comfortable urban thermal transport environment,which can further give new ideas for improving the urban environment,as well as provide a scientific basis and theoretical foundation for the comprehensive management and control of environmental pollution.