Effects Of Arbors In Campus Courtyard On Air Flow Field And PM_2.5 Pollution Distribution

The acceleration of urbanization process and the rapid development of industry have brought earth-shaking changes to people's daily life,while enjoying convenience,it has also brought a series of environmental problems.Among them,the problem of atmospheric suspended particulate matter pollution has become an indispensable part,and more and more experts and researchers begin to focus on this issue.Taking the courtyard of Shenyang Architectural University as the research object,this paper explores the optimal plant scale and plant spatial layout based on PM2.5 reduction through field monitoring and CFD numerical simulation,which provides a scientific basis for plant planning and design from the perspective of air quality optimization,and also provides a new idea for the study of garden plants.The main results are as follows:(1)In the monitoring results,the diurnal variation of PM2.5 concentration in the courtyard of Shenyang Architectural University in June,July and August is the highest in the morning,declining with time,reaching the lowest at 4:00 p.m.,and then rising slowly.The relationship between PM2.5 concentration and meteorological factors is positive correlation with humidity,negative correlation with temperature and negative correlation with wind speed.As far as the monitoring data are concerned,the change trend of PM2.5 mass concentration is basically the same every month,but there are great differences in the value of PM2.5 mass concentration every month.The average monitoring data in August is the smallest,and the average monitoring data in June is the largest.This phenomenon is closely related to the school's unique law of life time.(2)In the current simulation results,the concentration of particulate matter on the windward side of the building is lower than that on the leeward side;in the vertical direction,the concentration decreases gradually with the increase of height.In addition,comparing the numerical simulation concentration with the field monitoring concentration,it is found that there is no difference between them,which proves the accuracy of the numerical simulation method and the rationality of setting parameters.As for the area of pollutant dispersion,at H=1.5m cross section,the area of the high concentration area is the largest and most continuous,mainly in a planar distribution.With the increase of height,the high concentration area becomes a linear distribution,and then the linear distribution begins to decrease gradually,eventually showing a local punctate or patchy distribution.(3)Under H=1.5m cross section,the overall diffusion concentration decreases along the diagonal line of the courtyard in the six plans with triangular layout,and the high concentration is concentrated in the southwest side.As far as the concentration is concerned,the order is plan 2>plan 1>plan 6>plan 4>plan 3>plan 5.In terms of air flow field,the courtyard air flow mainly moves counterclockwise.In terms of speed,the lowest degree of wind fall is 2.934 m/s for plan 6 and 1.611 m/s for plan 5.Among the six plans with block layout,the overall diffusion concentration decreases along the east-west direction,and the location of high concentration is mainly concentrated in the southwest side.As far as the concentration is concerned,the order is plan 12>plan 8>plan 10>plan 7>plan 9>plan 11.In the air flow field,the courtyard air flow is more along the East and west sides of the flow,in terms of speed,the largest degree of wind fall is 8.180m/s in plan 12,and the smallest is 2.650m/s in plan 11.Maintaining the same plant scale,12 plans were divided into 6 groups according to different plant layout.Comparing the PM2.5 concentration in the courtyard under the cross section of H=1.5m,it was found that the PM2.5 concentration in the courtyard with triangular plant spatial layout was higher than that in the courtyard with strip plant spatial layout.In the plan of plant triangular layout,the five uneven coefficients and the maximum deviation degree are the smallest,and the second is the largest;in the plan of plant strip layout,the eleventh uneven coefficient and the maximum deviation degree are the smallest,and the twelfth is the largest.