| Global climate change poses increasingly severe challenges to the human living environment,especially the changes in the wind-heat environment in dense metropolitan areas,leading to the continuous deterioration of heat island effect,carbon emissions,energy consumption,air pollution,ecological environment and sanitary health environment.The research about human settlement environment combined with urban climatology has become a hot topic.China's high-density cities,which are in the stage of rapid development,are particularly worthy of attention.The complexity and diversity of their problems provide a rich sample for solving urban problems.Guangzhou,a core city in the Guangdong-Hong Kong-Macao Bay Area with subtropical climate,is a typical Chinese first-tier city with exemplary morphology and climatology.It has important specimen value for the morphological study of urban wind-heat environment.However,many urban blocks in China are rapidly formed within the framework of urban planning management lacking of systematic attention to their urban wind-heat environment issues.Furthermore,the current domestic and foreign evaluation research results based on wind-heat environment-related urban space morphology are mainly aimed at urban scale or block scale.Meanwhile,only the evaluation of some space morphological indicators is concerned,and there is still a large research gap between these indicators and their effective connection with the current urban design mechanism in China.This research aims at mesoscale urban spatial form,combined with urban climatology and other research methods,from a systematic perspective to carry out quantitative research on urban space morphology assessment based on the wind-heat environment and provide scientific and effective wind-heat environment assessment for urban design guidelines.Firstly,the research adopts classic urban morphological research methods such as Typo-Morphological Approach and takes Guangzhou as the research object to analyze the typical space morphology area under the influence of urban design mechanism,sustainable development space morphology model,and Guangzhou's regional settlement spatial characteristics.Based on the research of many cases,it is concluded that the three types of ‘mountain-front comb-type',‘waterfront comb-type' and ‘patch type' are the typical urban space morphology patterns currently being formed in Guangzhou.Subsequently,the components of the space morphology are analyzed,and an element system composed of three levels of ‘basic layer',‘spatial layer',and ‘active layer',4 elements and 10 detailed elements are defined.On this basis,with the principles of ventilation,heat dissipation,environmental cooling,and heat insulation as the goals,closely following the above three types of typical space morphological characteristics,the mechanisms related to the wind-heat environment are summarized.Secondly,the research constructs the evaluation method of urban space morphology related to the wind-heat environment:(1)Three levels of space morphological elements,comprehensive analysis indicators and methods related to the wind-heat environment are carried out;(2)The research sets the simulation experiment method by selecting analysis tools,and innovatively arranges points according to the structural characteristics of the urban space morphology;(3)The analysis tool ENVI-met was utilized to carry out on-site measurement and software simulation verification on 6 different test points in Baiyun New Town which is one of the typical space morphology type cases.Pedestrian space wind-heat environment measurements were carried out during the summer.At the same time,the experiment simulates the wind-heat environment of the measured area and analyzes the characteristics of the wind-heat environment with the help of the human thermal comfort index---physiological equivalent temperature(PET).Finally,it verifies the adaptability of the software simulation to different space morphological features and sets the boundary conditions of this simulation experiment.Next,based on the analysis methods,measured data and research tools of the above urban space morphological elements,the research first utilizes ENVI-met to simulate the wind-heat environment of 9 urban design cases containing 3 types of space morphology,and compare the wind-heat environment simulation results of different measurement points in various types of space morphology.Then based on the research of the main influencing factors of the wind-heat environment,the detailed analysis of the space morphological elements was carried out,then the methods of overall analysis verification,classification analysis verification and multi-level comparison were utilized to summarize the consistency law between the results.It was finally found that:(1)Space morphological elements and the wind environment simulation experiment analysis were utilized for different morphological types,and the results showed that the ranking of the two types of experimental analysis results in up to 90% of cases was the same;(2)Mountain-front comb-type space morphological elements have the greatest influence on wind speed.The average simulated wind speed results are 0.73 m/s,0.85 m/s,and 0.9 m/s,respectively.The difference in wind speed between different space morphological schemes is close to 25 %,and the fit between the valley trend and space morphological elements has a great influence on the simulation experiment results;(3)The wind environment simulation results of the three open cases are all optimal;(4)In terms of basic layer and space layer elements,three detailed elements such as natural resource utilization,primary cold source,and open space are essential.For example,if the simulation value of the average PET of the water-net comb structure drops to 44.54?,it is close to 1? lower than the average maximum value of other models;(5)In terms of active layer elements,two detailed space morphological elements,such as the underlying surface and shading conditions,play a key role in the final PET results.The paper finally reflects on the current urban design evaluation methods and discusses the methodological issues of modern urban design systems from a critical perspective.The index system of the three levels of space morphological elements is summarized.AHP,expert scoring,micro-climate simulation evaluation and other methods are utilized in combination with the objectives and tasks of different stages of urban design.Finally,an urban design evaluation method based on the comparison of multiple proposals is established.This research method incorporates a new system in the study of conventional urban space morphology,provides a scientific evaluation method for blueprint-style urban design proposal comparison and evaluation,and provides a new perspective for the research and control of high-density landscape cities. |
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