PIV study on characteristics of pedestrian-level fluctuating wind speeds around square buildings with different heights

Abstract

Flow fields around four square-section buildings with different heights in boundary layer flow (BLF) were captured by PIV tests to investigate the influence of an increase in building height on fluctuating wind speed fields and pedestrian-level peak wind speed around buildings. Flow visualization results indicate that upstream stagnation levels significantly increase with increasing building height, along with higher wind speeds in approaching BLF, causing stronger front downwash flows and upwash flows behind higher buildings. Variation in flow structures with building height significantly change pedestrian-level wind speed fields, including (1) causing a significant increase in mean wind speed on the sides of buildings, although their influence on turbulent kinetic energies (TKE) in the region is not obvious; (2) causing an increase in mean wind speeds and especially TKE downstream of buildings; Accordingly, high peak pedestrian-level winds for higher buildings occur not only in windy regions beside buildings but also in generally considered low-speed wake regions. This suggests that measurement of only mean pedestrian-level wind around buildings, especially super high-rise buildings, may not be adequate and might underestimate the influence of pedestrian-level winds on pedestrians. In addition, by zoning according to different fluctuating wind characteristics around buildings, peak pedestrian-level wind speed can be estimated by gust factor with better accuracy. Meanwhile, the influence of building height can be easily reflected by constant coefficients.