Study On The Optimization Of The Spatial Form Of Urban Block Under The Micro-thermal Environment

With the acceleration of urbanization,the energy consumption and carbon emissions of urban buildings are increasing rapidly,resulting in the various urban climate and environmental problems such as greenhouse effect,heat island effect,haze phenomenon and so on,which have a great influence on human life,production and habitat ecology.Advocating and implementing the concept of green,low-carbon and healthy sustainable urban design is a significant achievement to realize the national strategy of “carbon neutrality and carbon peaking” and alleviate global climate prroblem.As the basic component of urban space,the microthermal environment is an important part of the local climate of the city.The passive approach of optimizing the spatial distribution of neighborhoods to improve the thermal environment of neighborhoods and the comfort of pedestrians,promote the energy saving of neighborhood buildings and alleviate the urban heat island effect provides a green,efficient and low-cost method of "spatial-environmental" synergistic optimization.The first part of the thesis is a review of the theory and application of neighborhood spatial morphology in microthermal environments.The current research of microthermal environments in neighborhoods by domestic and foreign scholars is systematically summarized.According to the principle of similarity between urban canopy and porous media in geometric structure and physical properties and the validation and application basis of previous transformations of urban canopy topology into porous media,the fractal theory and the concept of fractal dimension are introduced.The qualitative analysis and quantitative calculation,analysis,verification and evaluation of the spatial morphology and layout characteristics of the neighborhood are systematically studied.The concept and framework of overall and single indicators are conceived to provide the theoretical basis for the subsequent research.The second part of the thesis is a study on the theoretical construction and the analysis of the measurement method of neighborhood spatial morphology under microthermal environment.The key indicators and concepts of fractal analysis of spatial morphology are clarified and explained,including the definition,classification,calculation method of fractal dimension and neighborhood morphological characteristics parameters(building density,street height-width ratio,green area),as well as as well as building height and street orientation,and the effects on the neighborhood.In addition,the fractal resolution mechanism under microthermal environment is also studied,and the evaluation indexes of microthermal environment dominated by wind and thermal environment are proposed.The Xinjiekou neighborhood is selected as a typical sample,and morphometric and microthermal environment simulation methods are applied to obtain the overall and single indicators of the Xinjiekou neighborhood,providing the foundation for later investigation on the influence of neighborhood spatial morphology on microthermal environment.The third part of the thesis is an analysis of the spatial morphology of neighborhoods and microthermal environment measurement methods..Taking Xinjiekou neighborhood as the sample,22 typical neighborhood types are further extracted and the spatial morphology of the neighborhood is measured by using the digital simulation platform.The overall and single indicators are obtained by calculation,and then a systematic setting and preliminary study on the measurement of microthermal environment including simulation methods(computational and physical models),parameter setting and working condition selection is conducted.It provides the basis of empirical parameters and platform guarantee for the subsequent research.The fourth part of the thesis is an analysis of the characteristic patterns of microthermal environment under neighborhood spatial morphology.Based on the results of the former two parts of the study,the basic characteristics,numerical ranges and influencing factors of the microthermal environment in different neighborhood spatial forms in the hot summer and cold winter areas represented by the Xinjiekou neighborhood spatial form sample are further analyzed in collaboration with the overall neighborhood spatial form index and single index bidirectional level.The derivation rules and influencing mechanisms of the microthermal environment in the neighborhood are revealed.The fifth part of the thesis is a modification study of neighborhood morphological indicators based on the actual measurements of microthermal environment.By comparing and analyzing the actual measurement and simulation results,it is found that the measured and simulated results are in good agreement,which indicates the feasibility and reliability of the numerical results.Based on the actual measurements,an assessment system based on the multiobjective elements such as wind,heat,safety and comfort all year round is proposed,and the numerical results are substituted into the assessment standard equation based on the actual cases,and the main indicators of the neighborhood morphology are revised.The sixth part of the thesis is to investigate the optimization strategy of neighborhood spatial morphology under microthermal environment and its demonstration application.Based on the results of the previous chapter,a comprehensive optimization objective of neighborhood microthermal environment and neighborhood optimization design principles are firstly determined,and then the results are summarized and sorted out at the level of neighborhood spatial morphology.For the overall indicators of neighborhood spatial form,single indicators and multi-indicator integrated action mechanism,the corresponding regulation strategies and optimization schemes are proposed to clarify the overall strategy of neighborhood form design optimization in an intuitive and detailed way.In order to verify the implementability of the strategy and the effectiveness of the optimization design,this work further selects typical urban center neighborhoods in hot-summer and cold-winter regions(Zidong core area and its Dongliu center neighborhood)as empirical samples and conducts simulation verification before and after optimization.The results show that the optimal design strategy proposed in this work can effectively reduce energy consumption in urban centers in hot-summer and cold-winter regions,improve urban climate comfort,mitigate urban heat island effect,and provide design reference and evaluation guidance for green,low-carbon and healthy sustainable urban design and neighborhood planning.