Study On The Influence Of SVF On Outdoor Thermal Environment In Residential Area

Under the global warming environment,people are paying more attention to outdoor thermal comfort in residential areas.Outdoor landscape planning is one of the effective ways to improve the outdoor thermal environment of the city.The sky view factor(SVF)is closely related to outdoor thermal comfort.Planting tree in residential areas can effectively change SVF and improve thermal comfort.This paper analyzes the relationship between tree and SVF in outdoor activity area,outdoor non-active area,and road green area in residential area in Guangzhou,and the impact on thermal comfort.(1)Measure the outdoor thermal environment of the four residential areas in Guangzhou.and calculate the evaluation criteria physiological equivalent temperature(PET)and wet bulb globe temperature(WBGT).The analysis shows that SVF on different underlying surfaces of green areas can effectively improve thermal comfort.The test results show that the lower temperature and humidity of the measuring point,the higher wind speed,so the smaller WBGT;the smaller temperature and SVF,the greater shading and the higher wind speed,so the smaller PET.For exposure underlying surfaces of similar SVF,the thermal comfort of the lawn is better than that of the hard ground.the smaller SVF of hard grounds exposed,the better thermal comfort.When the sunshade effect is good,the underlying surface has little effect on comfort.The shading of residential buildings is not as comfortable as the shade of trees.When the SVF is small and similar,the trees should be used as much as possible to reduce direct sunlight.According to the test data fitting the relationship between PET and SVF and dry-bulb temperature,the positive linear coefficient is up to 0.9,the smaller wind speed,the greater correlation.The positive linear coefficient of PET and SVF is above 0.63.The smaller windspeed,the greater radiation and the more relevant.The smaller SVF,the closer PET/Ta ratio is to 1,that is,the better the shading effect.High reflectivity Granite and concrete's SVF decrease,the PET/Ta decreased the most.(2)According to the standard,residential areas are divided into three levels: residential areas,community and group,green space is divided into public green,residential green,public green space and road green,Analyze the drawing of the residential area,and get the main shape and size of different green areas,and provide basis for determining the shape and size of the simulated working conditions.(3)Using ENVI-met software to simulate and analyze the relationship between SVF and thermal comfort in green areas.According to landscape planning method of the green space,the four types of green space are divided into: public green activity area,public green non-active area and road green.The simulation range of SVF is 0.2 to 0.7,SVF changes by changing the number of trees.The simulation results show that the SVF is smaller,the temperature is lower,the wind speed is higher,Tmrt and PET are smaller on common green space of same underlying surface.The SVF of the arbor+shrub+lawn combination in the non-active public green is small,and the thermal comfort is better.When the SVF was 0.22,the sunshade effect is good,the wind speed improves thermal comfort effect.the more bushes,the smaller Tmrt,but the smaller wind speed,the shrub coverage is too large,PET will increase.The common landscape of road green is tree+shrub,lawn or red brick,and the red brick has the worst thermal comfort,the more bushes,the smaller SVF,the better thermal comfort.Finally,simulate the improvement of thermal comfort under the optimal conditions in summer under extreme weather conditions.Tree + grass,tree + shrub + grass in the public green and the tree + shrub in the road green can effectively improve thermal comfort,and PET is only 3? larger than 30?.The results of research,testing and simulation can provide reference for design of SVF and planting of trees in the green.