 Abstract —The objective of this study is to conduct computational fluid dynamic (CFD) simulations for evaluating the cooling efficacy from vegetation implanted in a public park in the Taipei, Taiwan. To probe the impacts of park renewal by means of adding three pavilions and supplementary green areas on urban microclimates, the simulated results have revealed that the park having a higher percentage of green coverage ratio (GCR) tended to experience a better cooling effect. These findings can be used to explore the effects of different greening modifications on urban environments for achieving an effective thermal comfort in urban public spaces. Keywords—CFD simulations, green coverage ratio, urban heat island, urban public park. I. INTRODUCTION S urban development continues to increase, natural vegetation cover is being replaced with the constructed buildings and the infrastructure, forming a well-known heat island effect which can noticeably raise temperatures in densely built-up urban areas during the summer months. Urban parks are known to be useful for providing cool microclimates and mitigate the urban heat island (UHI) outcome attributable to the presence of vegetation cover. Various studies have been extensively conducted to utilize green space in moderating urban climates [1]. Researchers consistently suggested an effective way to alleviate the UHI effects via increasing tree cover area and density [2]. In recent times, the computational fluid dynamics (CFD) tool has become increasingly important to perform pre-evaluation and design simulations of quantitatively analyzing the cooling effect of green spaces in the development of urban planning. Several vegetation models were proposed and assessed in literature for reproducing the aerodynamic effect of trees on the airflow. In addition, to ease the urban heat island effect, Taha developed a vegetation model mainly classified as trees, green roofs and surfaces [3]. Bruse and Fleer utilized the microclimate CFD model, ENVI-met, to study the impact of ground coverage on thermal stress over a small park [4]. Dimoudi and Nikolopoulou employed CFD to An-Shik Yang is with Department of Energy and Refrigerating Air-Conditioning Engineering, National Taipei University of Technology, Taipei 10608, Taiwan (phone: 886-2-2771-2171 ext. 3523; fax: 886-2-2731-49191; e-mail: asyang@ntut.edu.tw). Chih-Yung Wen and Yu-Hsuan Juan are with Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (phone: 852-2766-6657; fax: 852-2365-47031; e-mail: cywen@polyu.edu.hk). Chiang-Ho Cheng is with the Department of Mechanical and Automation Engineering, University of Dayeh, Changhua 51591, Taiwan, (phone: 886-4-851-1888 ext. 2119; fax: 886-4-851-1224; e-mail: chcheng@mail.dyu.edu.tw). address the cooling effect of different vegetation arrangements in a generic building setup [5]. Alexandri and Jones conducted the CFD studies to describe the thermal influences of green walls and green roofs on the microclimate for nine different climates and urban canyon geometries [6]. Fröhlich and Matzarakis used the ENVI-met software to analyze the impacts of urban street design and surface material on the human thermal comfort [7]. Besides, Vidrih and Medved validated a three-dimensional CFD model by comparing the measured results with the predicted air temperatures in tree crowns, demonstrating the sufficiency of proposed CFD procedure to correctly simulate the thermo-flow processes in the city park environment [8]. Srivanit and Hokao focused on the strategies of greening modification through adding more greening area, including an on-site measurement and a numerical simulation model that uses ENVI-met [9]. The goal of this research is to perform CFD simulations for assessing the vegetation efficiency of a public park (with different greening types, e.g. trees and plants, green roofs, vertical green walls and grass lawns) and its influence on the atmosphere of bordering locality in a densely urbanized area in Taipei, Taiwan, which has a hot and humid climate. Numerical simulations were extended to investigate the influences of adding three pavilions and supplementary green areas on urban microclimates during the park renewal. The findings of this research will support better prediction of the influences of park renewal and spatial arrangements of different greening modifications, helping urban planners and managers mitigate increasing temperatures associated with climate change as well as to achieve an effective thermal adaptation of urban public spaces. II.DESCRIPTION OF BUILDING MODEL Xinsheng Park in this research was part of the urban redevelopment project in Taipei, Taiwan. Taipei City Government has unveiled three new pavilions (“Pavilion of the Future”, “Pavilion of Angel Life” and “Pavilion of Dreams” in the park for the 2010 Taipei International Flora Exposition. These pavilions were designed by the local architect Chang Ching-Hwa and constructed around old trees with their rooftops and walls populated by vegetation. After the expo, all fair pavilions were arranged to serve as activity venues for public events. During the park renewal, considerable endeavors were made to preserve the original condition of the park with main improvements of adding more green areas. The key vegetation design factors with different greening types were to have a positive impact on users’ comfort level by decreasing the air temperature. Fig. 1 demonstrates the aero-photographs of CFD Simulations to Study the Cooling Effects of Different Greening Modifications An-Shik Yang, Chih-Yung Wen, Chiang-Ho Cheng, Yu-Hsuan Juan A World Academy of Science, Engineering and Technology International Journal of Environmental and Ecological Engineering Vol:9, No:7, 2015 825 International Scholarly and Scientific Research & Innovation 9(7) 2015 ISNI:0000000091950263 Open Science Index, Environmental and Ecological Engineering Vol:9, No:7, 2015 publications.waset.org/10001624/pdf