The Architectural And Environmental Characteristics Of The Flow Between The Building Arrays And The Influence Of Pollutant Diffusion

With the rapid development of society,more and more people have completed urbanization.Due to the shortage of land resources,in order to meet the housing requirements of residents,a variety of different layout of urban buildings emerge in an endless stream.According to the 2019 Bulletin on the State of China's Ecology and Environment,only 157 of the country's 337 prefecture-level cities meet environmental standards,accounting for 46.6 percent of all cities.It can be seen that the diffusion of pollutants in the atmosphere has a more serious impact on the urban environment.The surrounding area of urban buildings is the main activity scope of residents' production and life,so the research on the environment of people's walking style and the characteristics of pollutant diffusion in the surrounding area of urban buildings is the key content of current research.In this paper,CFD numerical simulation technology is used to study the flow field and concentration field inside the block from the perspectives of architectural complex structure and environmental factors.Firstly,this paper summarizes the current situation of the study on the wind environment and pollutant diffusion in the inner blocks of building groups at home and abroad,and introduces the basic theoretical knowledge of wind tunnel experiment and numerical simulation.Then,the wind tunnel experiment about the buildings done by predecessors is verified by numerical simulation.The calculated results are compared with the experimental data to verify the correctness and effectiveness of CFD technology.Secondly,this paper focuses on four different building layouts,and discusses the influence of four building heights on the gas flow and pollutant diffusion in the target street canyon under each layout,and studies the influence of building height changes on the wind pressure coefficient under the typical determinant building layouts.The results show that the maximum wind speed ratio at the pedestrian height 2m in the central area of the target street valley is about 1.9 times of that at the longitudinal distance W of 2H when the transverse distance S is 2H.The maximum Kc at the height of 2m in the leeward area is 0.7 times that when W is 2H.Under the four building layouts,the maximum wind speed of the staggered layout at the pedestrian height 2m inside the street canyon was greater than that of the column layout,and the pollutant concentration in the windward area inside the street canyon was the lowest.Finally,according to the external environment,two different inlet wind directions(0°,45°)and three provenance positions were considered based on the working conditions above.It is found that when the wind direction is to the side,the area of the low wind speed area on the upper side of the building group increases first and then decreases with the increase of the building height,the diffusion range of pollutants near the target street valley decreases,and the high concentration value is almost only accumulated on the leeward side of the target street valley and the upper side wall.It is found that when the source term is located at S1,the pollutant has the least influence on the target street valley.The maximum leeward concentration of the source term at the position of S3 is about 100 times that of the maximum concentration of Kc at the position of S1.