| Under the background of global warming and the acceleration of China’s urbanization process,the urban heat island effect has been continuously enhanced,which has further deteriorated the urban living environment and lowered the quality of the living environment in urban areas.Alleviating the urban heat island effect and improving the urban living environment have become the most urgent issues facing urban development today.Urban public green space plays an important role in mitigating the heat island effect and affecting the outdoor thermal environment.City parks are an important part of urban public green space,and also a public place where a large number of urban residents will choose to conduct outdoor activities.An important factor that attracts people to stay and stay in a city park is its outdoor thermal comfort.At the same time,outdoor thermal comfort is also an important criterion for evaluating the livability of the urban environment.This research adopts a combination of on-site meteorological monitoring and subjective questionnaires.The people’s park in Chengdu,China is selected as the research object.The thermal comfort performance of different types of landscape spaces in the park during the winter and summer seasons is the main research content.And summarize the existing problems of outdoor thermal environment in People’s Park.At the same time,the thermal environment of the park was numerically simulated using CFD simulation software PHOENICS,and a corresponding optimization strategy was proposed based on the status quo.The field survey was conducted in the coldest and hottest months in Chengdu,and research was conducted in January and July 2019,respectively.Based on the thermal sensation data obtained from the local residents,their outdoor thermal environment was evaluated for comfort.On this basis,the CFD simulation software PHOENICS was used to carry out numerical simulation of the optimization strategy,and finally an optimization scheme was proposed and verified.The results show that in urban parks,increasing wind speed in summer and intensifying solar radiation in winter can effectively improve outdoor thermal comfort.The main research conclusions of this study are:（1）Different types of landscape spaces have different thermal comforts;（2）Air temperature is the most important factor affecting outdoor thermal comfort;（3）For the thermal sensation judgment of outdoor thermal comfort research in Chengdu area,ASHRAE 7-sites scale can be used;（4）The neutral temperature range of PET in Chengdu is（Winter: 6.9-18.2 ℃,Summer: 11.2-20.5 ℃）,and the neutral temperature range of UTCI is（Winter: 13.8-23.5 ℃,Summer: 22.8-28.2 ℃）;（5）Universal Thermal Climate Index（UTCI）is the best index to evaluate the outdoor thermal comfort of the human body in Chengdu;（6）In terms of planting,the main needs are shade in summer and light transmission in winter.Deciduous trees with good cooling and humidifying effects and wide canopy coverage areas are selected as the main tree species for greening;（7）The roof greening of the building should be increased,and the underlying surface of the park should be dominated by vegetation or water bodies,to avoid the appearance of a large area of open space.（8）Establish an air channel connecting the park and the city block in space.The shape and length of the air duct adopt trapezoidal shapes,which will help improve the air velocity in the park.These research results provide theoretical benchmarks and technical references for urban planners and landscape designers to optimize outdoor thermal comfort in urban areas so that they can create a more comfortable and healthy living environment for urban residents. |
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