Abstract
In the underground space development of residential areas, outdoor thermal environments at the pedestrian level greatly depend on the ground greening configuration, which is in turn affected by the overburden thickness of the underground space (OTUS). However, few studies have considered the effects of OTUS on the ground greening configuration and the further effects of the ground greening configuration on the outdoor thermal environment. This study aimed to provide insights into the design of OTUS for improving outdoor thermal environments. Two residential areas with row and enclosed layouts in Nanjing, China, were numerically studied using the computational fluid dynamics (CFD) simulation software ENVI-met. Outdoor thermal environments in the two residential areas, which had the same greening coverage rate, were simulated under different OTUSs and ground green configurations. The results indicate that to create a comfortable outdoor thermal environment, the OTUS should be designed to satisfy the requirement for planting small trees. If this requirement cannot be adequately satisfied, individuals can also set up tree wells or add soil on top of underground structures to plant small trees, and establish an OTUS that can satisfy the requirement of planting large shrubs in other areas.
Highlights
In recent years, with the rapid development of urbanization in China, there have been increasing problems related to the urban heat island effect during summer [1,2]
Taking the row layout as an example, the maximum average air temperature for large shrubs was 0.20 ◦C (15:00 p.m.) and 0.14 ◦C (14:00 p.m.) lower than those for lawns and small trees, respectively. These results indicate that in the underground space development area, the heat island effects can be effectively reduced by implementing an OTUS that satisfies the requirement of planting large shrubs
We chose two residential areas with row and enclosed layouts in Nanjing, China, as the research objects and used the computational fluid dynamics (CFD) software ENVI-met to quantitatively analyze the outdoor pedestrian-level thermal environment changes under three greening configurations—lawns, large shrubs, and small trees—with the same green coverage and to provide suggestions regarding the design of the OTUS based on the simulation results
Summary
With the rapid development of urbanization in China, there have been increasing problems related to the urban heat island effect during summer [1,2]. The urban heat island effect can reduce the outdoor thermal comfort of urban residents [3,4], increase the energy consumption from air conditioning in buildings [2,5], and even lead to fatalities [6,7,8,9]. Increasing ground greening coverage can effectively mitigate the heat island effect by providing shade and reducing the surface temperatures of the ground and buildings [2,3,11,12,13]. The influence of residential greening on outdoor thermal environments has been studied extensively, few studies have qualitatively discussed the influence of underground space development on residential greening and outdoor thermal environments [19,20,21,22] and even fewer have discussed this topic quantitatively [23,24]
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