Experimental study on cross-ventilation of a generic building in highly-dense urban areas: Impact of planar area density and wind direction

This study presents the experimental results on cross-ventilation in a generic low-rise building placed in highly-dense urban configurations. Flow visualization studies were conducted by utilization of a smoke generator in order to investigate the nature of the flow pattern inside and around the cross-ventilated building. Moreover, distribution of the wind surface pressure coefficients over windward and leeward facades and internal walls of the target building were measured using a pressure tap system. Furthermore, the airflow rate crossing through the openings was measured using a tracer gas method. Different building configurations, representing highly-dense urban areas, as well as different wind angles were investigated in this study. Surprisingly, the experimental results reveal a noticeable difference between the mechanism of cross-ventilation in moderately-dense and highly-dense buildings arrangements. A clear leeward jet with a highly-transient nature can be observed, which is generated due to a leeward vortex formed by the target and downstream buildings. As another novel finding of this study, the cross-ventilation is understood to be highly transient in highly-dense urban areas with a strong periodic fresh air pulsation through the windward and leeward openings. This behavior is fundamentally far from the steady state models considered for such cross-ventilation scenarios in literature.