Influence of Grass Lawns on the Summer Thermal Environment And
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Wang et al. Herit Sci (2021) 9:7 https://doi.org/10.1186/s40494-020-00479-9 RESEARCH ARTICLE Open Access Infuence of grass lawns on the summer thermal environment and microclimate of heritage sites: a case study of Fuling mausoleum, China Xiaoyu Wang* , Peng Liu and Gongwen Xu Abstract The thermal environment and microclimate of heritage sites has been severely impacted by rapid urbanization. This study collected various meteorological measurement data as a reference for computational fuid dynamics (CFD) simulation settings. Then CFD was applied to simulate the impact of lawns on the thermal environment and micro- climate of Fuling Mausoleum. We found that lawns and soil can cool the air through evaporation, and thus have a specifc cooling efect on the bricked ground. Simulations with the lawns, the bricked ground temperature decreased by 1.56–17.54 °C than that simulations without the lawns at 14:00, a decrease of 2.68%–24.20%. Under normal circum- stances, when the wind speed or relative humidity increased, the ground temperature dropped. Greenbelt vegetation can adjust the microclimate and human thermal comfort indicators. The consistency of the diference between the actual measurement and the CFD simulation results shows that CFD simulation can thus accurately refect the inter- nal temperature feld distribution if the selection of simulation parameters is reasonable. Theoretical calculation and analysis, experimental measurement research, and modern computer simulation analysis methods applied together constitute a complete system for studying modern physical environmental problems and can provide reliable and economic results. Keywords: Thermal environment, Microclimate, Fuling mausoleum, Heritage site, CFD simulation Introduction Several adaptation measures have been put into prac- As a result of the rapid expansion of urban areas, herit- tice for their potential to afect the urban microclimate, age sites that were initially located in the suburbs or rural mainly to reduce high temperatures [2–6]. Te greening areas of many cities have gradually become important and vegetation of urban areas are the most investigated inner city areas. Te phenomenon of urbanization has adaptation approaches as they can reduce the sur- caused severe impacts and changes to the natural envi- face temperature of the surrounding environment [3, ronment, and the environmental landscape is also dete- 7, 8]. Te ambient temperature can also be decreased riorating. Te natural vegetation cover has been replaced by evaporation and transpiration of plants. Te main by buildings and urban infrastructure, which results in methods to study the efectiveness of vegetation in the well-known urban heat island efect [1]. mitigating the heat island efect are feld measurements [7, 9, 10], ground control experiments [11], and com- putational fuid dynamics (CFD) simulation [12–18]. Of these, CFD evaluates the efectiveness of vegeta- *Correspondence: [email protected] tion coverage in detail on the outdoor urban microcli- School of Architecture & Civil Engineering, Shenyang University of Technology, Shenyang 110870, China mate, which is an economical and practical method of © The Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. 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Hong and Lin [19] used relative humidity; and (4) Analysis and comparison of the outdoor thermal simulation platform to discover the actual measurement of microclimate with the human the infuence of the green layout on the outdoor envi- thermal comfort index value. ronment and pedestrian thermal comfort. Bruce and Fleer [12] used CFD and ENVI-met models to simu- Methodology late the microclimate and studied the impact of ground Study site greening on the thermal stress coverage of small parks. Shenyang is located in central Liaoning Prov- Dimoudi and Nikolopoulou [13] used CFD model to ince, southern northeast China (41°12′N–43°02′N, compare the cooling efect of diferent methods and the 122°25′E–123°48′E). Fuling Mausoleum is located in the vegetation arrangement in general building facilities. eastern suburbs of Shenyang. It is the tomb of the Qing Li and Yu [20] used CFD to simulate the thermal envi- patriarch Nurhachi and his queen Yehenala and is one ronment and residential microclimate around a single of the three mausoleums of Shengjing. Fuling Mauso- building. Tey verifed their simulation by comparing leum was built in 1629 and was completed in 1651. After between the measured data with simulated temperature a great deal of construction works during the Shunzhi, of the outdoor thermal environment around buildings. Kangxi, and Qianlong periods of the Qing Dynasty, a Bowler et al. [7] conducted an empirical study on the large-scale and well-equipped ancient emperor tomb efect of urban greening for cooling efect. Te main complex was formed. When it was frst built, it was emphasis of previous research is on the evaluation of called “Xianhan Mausoleum” or “Taizu Mausoleum”. In the indoor microclimate of heritage buildings and how the frst year of Chongde (1636), it was named “Fuling to improve the comfort of users. Corgnati et al. [21] Mausoleum”, which implies the long-lasting fortune of also described a methodology for evaluating the micro- the Qing Dynasty [26]. In 2004, Te Tree Mausoleums climate in museums between traditional convenience of Shengjing (referring to Fuling, Zhaoling, and Yongling and thermal comfort. According to European stand- Mausoleums), were included on the UNESCO World ards such as EN 15,251 [22], La Gennusa et al. [23] ana- Heritage Site List [27]. lyzed the indoor climate and indoor environment in Fuling Mausoleum has a detailed layout and distinct historical Italian buildings, including temperature and levels and has a total area of approximately 194,800m2. humidity. It is shaped like an inner city with an outer wall. It com- CFD technology involves the solving of various con- prises three parts—the front yard, the square city and servation control partial diferential equations describ- the treasure city—and it gradually increases in eleva- ing fuid fow, heat transfer, and mass transfer and the tion from south to north. Te mausoleum building com- visualization of the diferent solved fow or heat trans- plex remains relatively intact [28]. Tere are 32 existing fer phenomena. CFD technology, theoretical analysis ancient buildings, which are symmetrically distrib- and experimental research have become three essential uted with the Shinto as the central axis. It is a complex fuid mechanics research methods. Tese three meth- of imperial tombs that integrates the characteristics of ods complement each other [24, 25]. To our knowledge, the Manchu and Han ethnicities, which difers from the few studies focus on the outdoor thermal environment tombs of the Ming Dynasty and those built after the and microclimate for heritage sites. Because of urbaniza- Qing Dynasty [26]. Tis article focuses on the three main tion around heritage sites, the summer temperatures are buildings of Fuling Mausoleum: Stele Pavilion, Long’en increasing. Tis study focused on the cooling efect of Gate and Long’en Hall (Fig. 1). Te roads in front of the grassland and vegetation on the environment in summer. buildings are paved with bricks, and the grass lawns On the basis of actual measurement, the CFD simulation cover two sides of the bricked ground (Fig. 2). experiment was applied to analyze the cooling efect of the vegetation. On‑site measurements First, infrared images and precise measurements are July is the hottest month of the year in Shenyang. Te taken with an infrared thermal imaging camera to collect daily average temperature is between 28 and 29 °C, and various physical data in meteorology as a reference for the weather is usually in the range 24–32 °C. Te maxi- CFD simulation settings. Ten, CFD was used to simu- mum ground temperature can reach 63 °C. In July, the late the impact of lawns on the thermal environment and average wind speed is 3.64–3.86 m/s and the wind direc- microclimate of the heritage site. Te research includes: tion is mainly southerly [29]. On July 12, 2020, when (1) Analysis and comparison of the actual measurement feld measurements were taken at Fuling Mausoleum, with simulation results; (2) Analysis of the simulation the weather was clear and the wind speed was relatively results before and simulations with the lawns; (3) Analy- low. To study the impact of lawns on the summer thermal sis of the simulation results at diferent wind speeds and environment and microclimate of Fuling Mausoleum, the Wang et al. Herit Sci (2021) 9:7 Page 3 of 16 Fig. 1 The main buildings of Fuling Mausoleum (white is the CFD simulation model) project team members selected fve-time points—10:00, imaging photos were taken to determine the real- 11:00, 12:00, 13:00, and 14:00—and conducted the feld time temperature at each measurement point.