Study On Optimization Simulation Of Urban Green Space Thermal Comfort Based On Sky View Factor(SVF)

With the acceleration of global warming and urbanization,the problem of urban thermal environment is becoming more and more prominent,and the thermal comfort of outdoor public space is also reduced.As an important part of urban public space,urban green space has various functions such as cooling and humidifying,regulating local microclimate,etc.Vegetation in green space can relieve thermal discomfort through evaporation and transpiration,regulating wind direction and blocking solar radiation,which can help mitigate the deterioration of thermal environment.Sky View Factor(SVF)is widely used in urban microclimate studies as an important indicator to characterize the intensity of solar radiation to the environment.Therefore,this paper takes urban green space in Xinxiang city as the research object,takes SVF as the thermal environment regulation index of urban green space,analyzes the relationship between SVF and thermal environment parameters in urban green space through field measurement and ENVI-met software simulation,and studies the improvement effect of SVF on thermal comfort under different structural characteristics of trees in green space.Finally,the urban green space thermal discomfort environment is optimized and enhanced based on the study outcomes.The results of the study show as follows.(1)SVF is significantly correlated with air temperature,relative humidity,wind speed,solar radiation intensity and Physiologically Equal Temperature(PET)in park green space and residential green space,while road green space is significantly correlated with air temperature and relative humidity only.All three types of urban green spaces show better thermal comfort in low SVF areas.(2)The thermal comfort environment of park green space is most influenced by SVF,and the low SVF area can keep the thermal feeling of the park within the range of "warm";the thermal comfort of residential green space is more influenced by building shadows,and under similar SVF conditions,the thermal comfort condition of the area with large building shadows is better;the thermal comfort of road green space differs in different road orientations.Under the same level of SVF,the thermal comfort of south-north orientation roads is better than that of east-west orientation roads.The regression fitting of SVF and PET for the three types of green areas show the best fitting results for all three functions.(3)Different structural characteristics of trees have an effect on the improvement of thermal comfort in urban green spaces.As the ratio of crown width to branching height(Crown Diameter/Branching Position Height,D/PH)increases,the effect of thermal comfort improvement gradually increases.Among the nine scenarios simulated,when D/PH=5.5,the average SVF of cylindrical canopy is the lowest and the thermal comfort improvement within the scenario is superior.(4)The optimization case reveals that the thermal comfort of urban green space can be improved by planting plants with wide crown and low branching position height in the future urban green space construction.The research results are supplement and development of the research related to urban green space microclimate and outdoor thermal comfort,which can provide reference and basis for future climate-adapted urban green space construction,and are of important theoretical and practical significance for improving the quality of urban spatial thermal environment.