Wind tunnel experiments on pumping ventilation through a three-story reduce-scaled building with two openings affected by upwind and downwind buildings

Abstract

Periodic vortex shedding from the building can induce pumping ventilation (PV) and promote the ventilation rate of single-sided ventilation with well-arranged open windows. The present study aims to investigate the influence of sheltering conditions (presence of upwind and/or downwind buildings) on pumping ventilation using wind tunnel experiments. Different building gap aspect ratios and sheltering conditions were considered as main influencing factors.The mean streamwise velocity and velocity fluctuation around the target building were measured. The oscillation frequency of pumping ventilation was obtained from the time history of window center velocity. The effective ventilation rate was utilized to quantify the ventilation effectiveness of pumping ventilation through constant-injection tracer gas method.The experimental results show that the influence of upwind building on the mean velocity and velocity fluctuation are much more significant than that of downwind building. The presence of upwind or downwind building can reduce the pumping ventilation frequency compared with the isolated case. The downwind building has larger reduction effect on PV frequency of the target building compared with the upwind building. Increase of gap aspect ratio could linearly promote the PV frequency. Sheltering could promote the effective ventilation rate of pumping ventilation compared with the isolated case and the ventilation rate could be overall the highest when sheltered by both upwind and downwind building. Upwind building has much larger effect on the concentration fluctuation inside the target building than downwind building. The findings of this study may help to better understand pumping ventilation mechanism in urban areas.