City Heat Environment Research Based On Remote Sensing And CFD Simulation

In hot-summer and cold-winter zone in our country, Human in quite some cities is confronting the challenge of living difficulty due to the dramatically changing climate. Related problems including living situations ( especially in summer ) and heat environments are becoming a focus. The problems of city heat environment include city climate, city planning, city underlying surface and so on and are related to multidisciplinary fields. Basing on Wuhan, a typical city in hot-summer and cold-winter zone, the research presents the digit technologies on remote sensing (RS) and computational fluid dynamics (CFD) and a detail was shown in the running status of the heat environments and structure of heat islands. Other aspects including analyzing the structure of heat islands and seeking for corresponding measures in urban planning are also displayed.The RS technology shows the advantages of a comprehensive and periodical observation and the thermo-infrared of RS image using to inverse the surface temperature, the evapotranspiration and the vegetation index, as well as to conduct the environment analysis in accordance with the property and structure of underlying surfaces. Furthermore, the RS technology is capable of reversing the parameters and results for the CFD technology. The CFD has the advantage of conducting fluid analysis. It can present the relationship of a distinct boundary layer in the city atmosphere, the heat environment and the running status of heat islands using the simulation of wind. Additionally, it can evaluate the design of the conception and optimization via simulation. Combing both technologies on studying heat environments would support with one another and thus is a tight research system. Basing on such a thought, the main work of the dissertation is show as follows.(1)Firstly, the derivation, background and definition of the heat environments are studied, followed by summarizing relevant literatures. It can be concluded that such a research has its unique. Though there have been some digitization methods available, some are limited to the single subject and thus are lack of comprehensive studies with multidisciplinary backgrounds and comprehensive technologies. This is one of flashpoints in this dissertation.(2)Quite some issues relating to the heat environment are mentioned, such as the climate, atmospheric boundary-layer, underlying surface and the index of heat environments. The heat environment can be derived from the boundary layer and is influenced by the climate, underlying surface and so on. We are trying to find the relationship among the heat environment, city climate and the underlying surface using a systematic analysis and correspondingly establishing a foundation for the subsequent digitization.(3)A digitization method for the research of city environment is established. Such a method combines the RS with the CFD expect for the data collection. The RS is used to study the heat environment by inversing the land-surface temperature and the evapotranspiration, and by combining underlying surface's parameters into research. Meanwhile, the CFD is used to simulate the heat environment by setting up a digital and fluid model.(4)Basing on the digitization method, the RS-based heat-environment research is conducted. Such studies include these steps such as the choice of RS images, data pretreatment and land-surface temperature inversion. The relation between heat island and underlying surfaces are discussed, including the underlying-surface index and extraction. Moreover, the structure of the heat island and the typical surface are also presented using Wuhan as the reference. As a result, there are complete researches on various stages and cities which cover in hot-summer and cold-winter zone. The evapotranspiration of the natural surface is also carried out. Although the evapotranspiration can not directly reflect the heat situation, it absorbs heat and thus improves the heat environment. Thus, such a method can be used to increase the accuracy of the CFD simulation. The model of acquiring the evapotranspiration, the running process and relationship with the surface temperature is discussed.(5)Based on related conclusions, the study examines boundary condition settings of CFD simulation, which is the key of the CFD simulation. The setting of traditional boundary conditions is simple but is lack of precision. To overcome such drawbacks, we have modified the setting by using the RS technology, thus making the simulation better matching to the structure and characteristic of heat islands. (6)Using the digital model reversed by the RS technology, the study also surveys the heat situation, the relation between the water body and the heat environments, and the ventilation panel basing on the study results of flowing in the motion of atmosphere. The CFD is found suitable for the problem well in terms of flowing and thus is a new and efficient way regarding the analysis of the wind environment, the temperature field, the living environment and the heat-island condition.The study of the heat situation basing on the spatial information technology is efficient in city environmental management and control. It is an important field in city planning and environmental sciences. The RS and the CFD technologies using in the study are less used for real planning projects. In the precondition of scientific planning methods mentioned greatly by local government, promoting this research method and combing it with real planning project appear to be meaning.