Effects of building height and porosity on pedestrian level wind comfort in a high-density urban built environment

Pedestrian level wind environment is affected by stagnated airflow in high-density cities. This study provides an understanding of the effects of building height and porosity size on pedestrian level wind comfort. The computational fluid dynamics (CFD) technique is utilized to reproduce wind flow around buildings at pedestrian level, and new wind comfort criteria for a low wind environment are adopted to evaluate wind comfort. More specifically, the Steady Reynolds Averaged Navier-Stokes (RANS) renormalization group (RNG) k-epsilon turbulence model is employed in this study, and the accuracy of the simulation results are assured by validation against the wind tunnel test data. The influence of different building heights and porosity sizes on wind comfort around an isolated building and a group of buildings are subsequently examined. It is shown that an increase building height could improve wind comfort inside the site boundary for both the isolated building and group of buildings. Furthermore, the wind comfort benefits increased when porosity is on the first floor compared to when it is on the second floor. Moreover, larger porosity size generally results in better wind comfort than smaller porosity size. From a practical view point, this study provides information for city planners and architects to use in the improvement of pedestrian level wind comfort, without losing land use efficacy.