The Influence Of Different Urban Block On Wind And Pollution Fields

With the rapid development of China's economy,the layout of urban buildings is becoming more and more intensive,the number of motor vehicles is increasing,and the problems of urban motor vehicle exhaust pollution are becoming more and more prominent.In order to study the wind field and pollutant transfer characteristics,the computational fluid dynamics software FLUENT with RNG ?-? turbulence model was employed to simulate the three dimensional wind speed,turbulent intensity and pollutant concentration around urban block.Firstly,the numerical experiments are compared with the results of wind tunnel experiments to verify the numerical scheme used in this paper is reasonable.On this basis,based on the typical urban street canyon,the modeling of non-isolated three dimensional regular and staggered block.As the research object,respectively,simulation of the two city street canyon building layout inside and under the direction of the wind field,and the vehicle straight across the road when the pollutant concentration distribution,and the distribution of flow field and pollutant concentration are explained.The results show that whether it is regular or a stagger layout,the inflow of air due to the blockade of the buildings,have led to the construction of buildings in the direction of low wind speed vortex area,and gathered a large number of pollutants from within the block.Neighborhood wind speed near the entrance,by the narrow tube effect,the formation of the maximum wind speed area,the corresponding concentration of pollutants the lowest.Consistent with previous studies,a clockwise vortex was generated in the street canyons with an aspect ratio of 1,and the contaminants were mainly concentrated in the leeward surface.The diffusion of pollutants is closely related to the turbulence intensity and wind speed.In the high turbulence region and the wind speed area,the contaminant concentration is lower,and the pollutant concentration in the leeward area is higher.For the staggered layout of the urban block,we can find wake interference flow and eddies when the street canyon aspect ratio of 1:3.According to the staggered urban block of statistics of the target street,we can find that the wind speed in the windward area,the central area and the leeward area is basically the same,and the layout of the staggered block is better.The turbulence intensity in the central area is slightly larger than that in the windward area,and it is larger than that in the leeward region.The concentration of pollutants in the windward area is the highest,the center area is the second.Based on the comparison of the two typical blocks,the wind speed,turbulence intensity and pollutant concentration of the staggered urban block in the target street canyon are larger.The results of this study can provide a scientific basis for rational design of street layout,accurate prediction of pollutant concentration distribution and utilization of natural wind to alleviate air pollution in urban high density areas.