Paper Title
STUDY ON THE INFLUENCE OF THE LIFT-UP BUILDING CONFIGURATIONSON URBAN MICROCLIMATE AND NO2 POLLUTANT

Abstract
Abstract - Global urbanization has intensified the urban heat island effect and extreme weather conditions, making resilient cities an important issue. In tropical and subtropical climate zones, lift-upbuildings are common in Hong Kong and Singapore to cope with high temperatures and heavy rain in the summer. Previous studies have shown that combining lift-upbuildings with modern high-rise building planning is an important strategy for creating a distinctive urban landscape and improving pedestrian wind and comfort, mainly targeting the microclimate around single buildings, but there is little research on the microclimate at the urban scale. Therefore, this study referred to Yu-Hsuan Juan et al. (2021) Ideal City 6X6, which sets four types of building arrangements: original (160m), staggered (160m), low in the front and high in the back (105-160m), and staggered low in the front and high in the back (105-160m). A total of eight schemes were simulated using CFD ANSYS Fluent v18 computer modeling, including no perforated buildings and all areas with lift-upbuildings (referring to the optimized form in the study by Ying-Ming Su and Shin-Di Shih (2021) (buildings retreated by 10% on all sides – twostories perforated)), to investigate the impact of lift-up buildings in high-density urban areas on urban wind and NO2 pollutant levels.The simulation results show that in high-rise and high-density urban areas, the group of lift-up buildings has better ventilation effects on microclimates compared to non-ventilated buildings. Among the four groups of ideal city layouts with lift-up buildings, the average wind speed increases in the following order: original group (17%) > front low and back high group (6.3%) > front low and back high staggered group (4.3%) > staggered group (1%). The original group with better ventilation effect has the highest percentage increase in average wind speed at three heights: pedestrian height of 1.5m (29%) > ventilated height of 7.8m (19%) > building height of 105m (2%). This indicates that the impact of lift-up design on urban wind fields decreases as the vertical height increases. The average wind speed at the pedestrian height of 1.5m is 0.71m/s, which is 29% higher than that of non-ventilated buildings. The average wind speed in the middle-lower wind zone is 0.54m/s, which is 50% higher than that of non-ventilated buildings, indicating that lift-up buildings can reduce wall effects and increase wind speed in the middle-lower wind zone. The pollution simulation results of the original group show that after ventilation, pollutants significantly reduce in the downwind side of the city and the leeward side of the buildings, which is negatively correlated with wind speed. Therefore, it can be concluded that the configuration of lift-up buildings in the original ideal city has a relatively better wind speed increase and has a significant improvement in the overall wind field and pollution reduction ability. Keywords - Urban Heat Island, Lift-Up Buildings, Urban Microclimate, Computational Fluid Dynamics (Cfd).