Computer-Aided Simulation Analysis on the Impact of Various Opening Patterns in High-Rise Opening Building towards Pollutants Dispersion

Abstract

Taiwan is the fourth most urbanized country in Asia, where the urban spatial structure of high-rise and density hinders urban ventilation. Studies have proven that opening buildings reduce the area of windward surfaces, which can effectively mitigate the urban heat island effect and disperse pollutant accumulation. Until now, most researchers have discussed the differences in heights and sizes of openings in the opening buildings, but few discussed the influence of opening patterns on urban ventilation. Thus, we set the building unit to 30 × 30 m with 160-m height with the opening height as tall as 0.45 times the building height and a 9% opening rate, distributed in 6 × 6 ideal city configuration Four cases (case A: no opening, case B: middle square, case C: right square, and case D: middle rectangular) with different arrays of opening buildings were compared with ANSYS Fluent v18 to simulate the wind environment and NO2 pollutants. The results showed that the opening building improved the permeability of street ventilation and air circulation, which greatly increased the wind speed at a height of 72 m. The distribution of pollutants was affected by the distance from the pollution source and the width of the street. Pollutants were gradually dispersed as the height increased. Case D of a long-narrow rectangular opening (adjacent to the pedestrian floor) and the venture effects formed eddy currents above and below the opening, which effectively improved the ventilation in the street canyon. Therefore, it had the best wind speed on the pedestrian level among the cases. The wind speed of the 72 m-high floor was much higher than that of case A, and the vortex generated by the airflow flowing through the opening in the street canyon increased the diffusion effect of pollutants. Overall, the opening building with a rectangular opening was the optimum solution in terms of wind speed improvement and pollutant removal. In addition to the opening design in the building facade, it is recommended to provide sufficient open space to improve air circulation in the building block and disperse pollutants.

Keywords

• high-rise opening building
• urban street canyon
• traffic pollutant (NO₂)
• CFD analysis