Quantification Of The Openness Of Urban External Space Through Urban Section Based On Wind Speed

For the urban built environment,the morphological characteristics of the external space of the building are of decisive significance to the behavior,visual perception and comfort of the people living in it.However,external space is often confused with the concept of open space,which is based on the definition of physical attributes,while open space is usually defined by social attributes.In the study of urban physical environment,especially in the study of urban microclimate environment,the correlation between it and open space tends to produce deviation.Therefore,it is of great significance to directly and quantitatively describe the openness of the external space of a city based on physical attributes,so as to understand the relationship between urban form and microclimate.The existing quantitative research on the urban external space focuses on the external space categories with clear boundaries,such as streets and squares.However,due to the unclear features of the external space boundaries in complex urban forms,these quantitative analysis methods cannot be directly applied to the quantitative analysis of external space.Among these quantitative analyses,the aspect ratio is the most widely used index,and its correlation with wind speed has been proved.From the perspective of urban section,our research comprehensively consider the aspect ratio of the external space to its direction and the influence of wind speed,and taking the aspect ratio of different sections of the external space as the basic index to quantify the openness of the external space,we proposed three indexes: the aspect ratio(HWR),the directional aspect ratio(HWR_a),and the average aspect ratio(HWR_average).In addition,based on two different cutting methods of urban profile,rotary cutting method and parallel cutting method,five quantitative analysis methods of external space openness are proposed.Meanwhile,the steps of the five methods are introduced in detail with the data of examples and their differences in quantitative results and methods are compared respectively.Based on the results of the external space openness obtained by different quantitative methods,the spearman correlation coefficient is used to analyze the correlation between the results and the wind speed distribution of the external space,and the results show that there is a strong correlation between the quantified external space openness and the wind speed in this study.The correlation between different quantitative methods and wind speed also provides reference for the setting of relevant parameters and the selection of quantitative methods in all the quantitative methods.Finally,taking four typical plots with different textures in Nanjing city as the case study,the quantitative analysis method with the highest correlation between the quantitative results of external space openness and wind speed was selected to conduct a quantitative analysis on the external space openness of the four plots.Based on the results of quantitative analysis,the distribution characteristics of external space with different open degrees in each plot were analyzed,and the distribution differences in the four plots were compared.This study proposes a method of quantitative analysis of the openness of external space in complex urban morphology.The analysis results can help to improve the understanding of urban morphology and its relevance to microclimate,and provide support for relevant planning decisions.The whole thesis contains about 36000 words,62 pictures and charts.