| In the CBD(Central Business District), land resource is concentrated, value of development is high, and underlying surface environment is characteristic. A large number of office workers work in CBD, which also attracts many tourists as an urban landmark. In recent years of rapid development and construction of cities, the concept of ecological and sustainable development comes into focus. It is of importance to mitigate heat island effect and to optimize local thermal environment at the same time of planning and designing the high strength developed urban environment. Accordingly, this thesis conducted investigating, experimenting and simulating of the CBD, and studied from different levels, in order to get a intuitive understanding of thermal environment, to analyze main influencing factors of both the overall level and the block level, as well as to seek for planning and designing methods for thermal environment optimization of CBD.First of all, this thesis analyzed the planning and layout characteristics of domestic main CBD cases based on field and literature investigations. Control requirements in urban planning management documents were also researched and compared with the case investigations. The qualitative and quantitative value ranges of thermal influencing factors of both the overall level and the block level were studied.Second, the field measurement device of air temperature was simply improved. The natural ventilation device was improved to become a forced ventilation and radiation protection device. Comparative experiments were conducted to verify the accuracy of the new device applied to outdoor thermal field measurement. A typical block of Zhujiang New Town that is the CBD of Guangzhou city was chosen as the experiment object. The thermal field measurement lasted for continuously 47 hours was conducted, and outdoor microclimate data were obtained. Empirical research analysis was done from heat island intensity, thermal safety and thermal comfort aspects.Third, evaluation index of thermal environment were determined. A numerical simulation model was employed, and the simulating results were verified based on the measured experimental data. ENVI-met was chosen as the computing tool to simulate the overall thermal condition of the high strength developed urban environment in CBD during daytime.Then, cases of the CBD overall level were set up to represent different thermal influencing factors such as the axis, building layout, and green space layout. ENVI-met was employed to simulate these cases. It was found that green space layout was the most important factor, green axis was recommended and centralized layout should be avoided. Direction of the axis also played an important role, and the north and south direction should be avoided. The influence of building layout was relatively small.Finally, cases of the CBD block level were set up to represent different thermal influencing factors such as values of important planning index, building layout and green space layout. ENVI-met was employed to simulate these cases. It was found that different building layouts affected the roles of important planning index. It was an effective means to raise the FAR appropriately up to 6 or above. Increasing building density appropriately was also an important strategy on the premise of increasing FAR. Podium density more than 35% was recommended and 45% was the best for the block with tower and slab-type buildings. The larger the area of green space, the better the thermal environment was, and the arbor was the key to improve thermal environment. The green space should be avoided excessively concentrated. It was a better choice to arrange green space outside the building shadow so as to get more sun shade and consequently be helpful for improving the overall thermal environment. Besides, building layouts good and bad for thermal environment were put forward to offer references for planning and designing. |
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