Abstract:

Air pollution is a serious concern that causes adverse and harmful impact on living quality and human health. As pollutant transport is significantly affected by local wind conditions, it is necessary to understand thoroughly the transport mechanism associated with winds and turbulence so as to improve pedestrian-level air quality. There exist the inertial sublayer (ISL) and the roughness sublayer (RSL) in the atmospheric surface layer (ASL) where possess different dynamics. In this study, wind tunnel experiments are performed to characterize ASL winds and turbulence over real urban morphology. In the experiment, building models of downtown Kowloon Peninsula, Hong Kong are fabricated by 3D printing. Noticeable variations of mean wind speed u, fluctuating velocities u’’ and w’’together with vertical momentum flux u’’w’’ in the ISL and RSL are observed. Given the different transport mechanism in ISLs and RSLs, it is suggested that the aged air is removed by slow, massive updrafts accomplishing with slow, horizontal puffs and the fresh air is driven by spurlike downdrafts to street level.