基于热环境脆弱性的城市空间形态布局模拟优化

Urban heat island is the result of complicated interactions of numerous elements owned by urban thermal environment system. How to regulate it effectively has become a research hotspot nowadays. Thus, this project introduces vulnerability theory to the urban thermal environment study. Through a systematic analysis of the urban thermal environment, the dynamical structure model of the thermal environment system and the state space equations characterizing the system are built based on thermodynamic theory. Furthermore, the vulnerability mechanisms that facilitate the urban thermal environment system to be in the state of heat island are explored and the vulnerability quantitative model is built by analyzing the impact of the heat on the urban thermal environment system, the transmission and transformation among the elements of the system, and the change and response of the function and state of the system, which is intended to serve as methodology support to the researches of mechanisms and regulation on the urban heat island. Finally, taking Hongshan District, Wuhan City as the study area, the thermal environment numerical simulation model is built based on Computational Fluid Dynamics technique, and is coupled with thermal environmental vulnerability quantitative model. Then the thermal environmental vulnerability of the study area is simulated and optimized through changing the spatial conformation and allocation, which is to reduce the thermal environmental vulnerability and mitigate the heat island. The study would provide guidelines and technical supports to improve and optimize the urban thermal environment by modifying the inner structure of the urban ecological system.

城市热岛效应是城市热环境系统众多要素复杂作用的结果，如何对其进行有效调控已成为当前研究的热点。为此，本研究将脆弱性理论引入到城市热环境中，通过对城市热环境进行系统解析，以热力学理论为基础，建立热环境系统动力学结构模型与状态空间表征方程；进而分析热胁迫作用在热环境系统内部要素间的传递与转换及其系统功能状态的响应过程，剖析城市热环境系统容易处于“热岛效应”这一状态的脆弱性机制，建立热环境脆弱性量化模型，以期为城市热岛效应形成机理与调控的研究提供方法论上的支持。在此基础上，以武汉市洪山区为案例，基于计算流体力学技术建立研究区域热环境数值模拟模型，并与热环境脆弱性量化模型进行耦合。通过对研究区域进行空间形态布局调整与热环境脆弱性模拟计算优化分析，以实现热环境脆弱性的降低和热岛效应的减缓，为从城市生态系统内部结构出发进行改造实践以实现城市热环境的改善与优化提供指导方向与技术支撑。

城市热环境已经成为当前城市生态系统的重要和突出问题。对其进行有效调控对提升城市功能具有重要意义。本项目以热力学与动力学理论为基础，通过对城市热环境进行系统解析，建立城市热环境动力学结构模型。在此基础上对城市热环境的脆弱性进行分析，通过改变相关因素的状态值以分析城市热环境系统温度参量的响应（敏感性等），对各个因素状态值变化引起的温度变化大小进行定量分析。进一步基于WRF模式耦合城市冠层模型建立城市热环境数值模拟模型。以武汉市作为研究实例，通过调整改变城市的空间形态布局，具体主要调整建筑物和街道的宽度与走向以及筑物表面的反照率和屋顶绿化面积比例，然后模拟计算调整后的城市热环境状态参量，并对调整前后热环境主要状态参量（气温等）进行比较以分析热环境的改善效果。脆弱性分析结果表明，在人为可控的因素中，反照率与相对湿度对城市气温影响较大，可作为城市热环境调控重点考虑因素。热环境空间形态布局模拟结果表明调整街道与建筑物的走向与宽度以顺应风的流动有一定的降温效果，但总体来说降温效果不够明显；提高建筑物表面的反照率对整个区域来说白天都有较好的降温效果；采用屋顶绿化对于夜间降温具有较大的优势。相关研究结果可为城市热环境改善的实践提供参考，对于已建成区域，采用高反照率表面材料和屋顶绿化是较为行之有效的措施；对于新城区建设，则可在此基础上进一步考虑街道与建筑物的走向与布局问题以实现热环境的进一步改善。