The Influence Of Sidewalk Greening On Thermal Comfort In Summer

With the acceleration of urbanization,urban hard elements increase,natural elements gradually reduce,energy consumption and more heat,resulting in the heat island effect and other environmental problems,especially in summer,affecting the physical and mental health of urban residents.Therefore,the study of urban microclimate has attracted the attention of contemporary scholars.Sidewalk is an important outdoor activity space in the city,which is closely related to the life of urban residents.Its thermal comfort is of great significance to the development of urban outdoor space.In this paper,the design of sidewalk greening in Tianjin city is taken as the research object,and the thermal environment of sidewalk is studied through measurement and simulation,which provides theoretical guidance and practical strategy for the optimization strategy of sidewalk greening in Tianjin and other areas.The research is mainly carried out from three research questions.Firstly,on the basis of field investigation and relevant theoretical analysis,the regulation degree of typical street tree species on sidewalk thermal environment and thermal comfort in Tianjin is quantitatively studied through measurement and ENVI-MET simulation.The interrelationships between leaf area index,branch point height and canopy width and microclimate factors and thermal comfort were analyzed.Secondly,after verifying the accuracy of the simulation,based on the situation of field investigation,the impacts of typical greening forms on pedestrian thermal environment and thermal comfort of three-board two-belt road and three-board four-belt road were simulated respectively,and the comparative analysis of the two road forms was conducted.Finally,the influence degree of different greenbelt widths on sidewalk thermal environment and human thermal comfort is simulated,and the critical value of greenbelt widths with better regulation degree on sidewalk thermal environment is obtained through data analysis.The results showed that:(1)The planting of street trees can significantly improve the thermal environment and thermal comfort of sidewalks in summer.Koelreuteria paniculata,the typical street tree species in Tianjin,had the best regulating effect on cooling and humidification and thermal comfort,followed by Platanus,Fraxinus chinensis,Robinia pseudoacacia,Populus,Styphnolobium japonicum and Juniperus chinensis;Different tree species in the summer on the thermal environment and thermal comfort control degree of difference,the leaf area index,height of branch points and the crown shape characteristic,the influence of temperature and humidification effect associated with the crown width,the wind speed value influenced by the branch point height,leaf area index,the branch point height,crown breadth,leaf area index of trees species,can effectively improve the thermal comfort of the summer,The correlation with lai was the highest.(2)In the form of road with three boards and two belts,the cooling effect is best in the straw structure,the humidification and wind speed regulation effect is best in the straw and high irrigation structure,and the thermal comfort improvement effect is best in the straw and low irrigation structure;In the form of three-board and four-belt road,under the same planting structure,the effect of cooling and humidification decreases with the addition of green belt,and the ability of regulating wind speed and thermal comfort increases with the addition of green belt.The structure with large trees on both sides is least affected by the planting form of tree pool or green belt.Under the same planting form,the best effect of cooling and humidifying and regulating thermal comfort was to plant large trees on both sides of the sidewalk,followed by the single-side planting of large trees and the single-side planting of large trees and the single-side planting of small trees and small trees.The thermal environment and thermal comfort of three-board four-belt roads and sidewalks are not necessarily stronger than that of three-board four-belt roads and sidewalks.(3)There is little difference in the degree of cooling and humidification and thermal comfort of the green belt with width of less than 4 meters;About 6 meters of green belt width adjustment effect is significant;The width of the green belt with a width of eight meters and above has the best effect on thermal comfort,but there is not much difference with that of the green belt with a width of six meters.The width of the green belt is about 6 meters,which is economical and has a better effect on the thermal environment and thermal comfort of the sidewalk.