The Impact Of Sky View Factor On Thermal Environment Of Urban Squares In Severe Cold Area

The urban square is an important part of the urban open space,and it is also a place where urban residents take daily outdoor activities.The physical environment of urban square affects the comfort of residents in the space,so it is closely related to the frequency of outdoor activities of urban residents.Due to the long and cold winter in severe cold area,extreme climatic conditions have caused many inconveniences to the outdoor activities of urban residents.Therefore,urban residents in severe cold area have an urgent need to improve the thermal environment of urban open spaces.Sky View Factor(SVF),as an influencing factor of urban heat island effect,is widely used in the study of urban microclimate.The existing research results show that SVF is closely related to the total amount of solar radiation received in the space.Therefore,a further quantitative study on the relationship between SVF and thermal environment parameters has theoretical and practical value for improving the thermal environment of urban squares in severe cold area.Firstly,this study sorts out the relevant research progress at home and abroad,analyzes and summarizes the existing theoretical achievements,and points out the limitations of the existing research.Through the investigation of satellite map,this paper makes a basic investigation on the urban squares of Harbin,a typical cities in severe cold area,and sorts out several kinds of plane shape data of the existing urban squares,which provides the basis for the follow-up study.Secondly,two groups of urban squares with the same enclosing interface and similar geographical locations with large differences in SVF are selected for field test of the thermal environment,which verifies that SVF has a significant impact on the thermal environment of urban squares.Finally,based on the survey results of urban squares,the ideal models of different square plane shapes,areas and opening dimensions are established in each SVF interval,and the method of improving the thermal environment by controlling SVF by changing the height of buildings around the square are explored.Based on the simulation results,the correlation between SVF and thermal environment parameters of urban squares in severe cold area was deeply discussed.(1)In the basic investigation and study,all urban squares in the main urban area of Harbin were selected,and various spatial morphological elements such as the block orientation,plane scale and side length ratio of the urban squares were extracted.It provides a basis for the selection of test sites for subsequent thermal environment measurements and the establishment of numerical simulation research models;(2)Among the mainstream SVF calculation methods,the two most suitable SVF calculation methods for this study are selected in combination with the research methods of this study,and the calculation results of the two calculation methods are compared and corrected;(3)The thermal environment of three squares with greening interfaces and two squares with buildings are measured and studied.Based on the measured results,the impact of SVF on urban squares with different enclosing interfaces in different seasons is explored;(4)Since the thermal environment of urban squares in the field test is influenced by many factors,it is impossible to quantitatively analyze the impact of SVF on the thermal environment of urban squares.This study continues to carry out numerical simulation research.Based on the basic research results and the characteristics of typical blocks in Harbin,the ideal models of25 city squares are established.This study quantitatively explores the influence of SVF on thermal environment parameters under different square spatial scales,which can provide data support for the subsequent evaluation of the environmental comfort of urban squares.The innovation of this study is to reveal the mechanism of SVF influence on the thermal environment parameters,including the effects of SVF on air temperature,relative humidity,mean radiation temperature,and wind speed in different seasons.This study fills the gap in the research field of thermal environment in severe cold areas.