Experimental study on mitigating extreme roof suctions by passive vortex generators

Abstract

High wind suction always occurs at the edges and corners of large-span low-rise flat roofs, which can lead to severe damage to roof elements and even to the overall destruction of the roof. The passive vortex generator (PVG), a new device which can generate streamwise vortices, is proposed to mitigate the extreme wind suction on a low-rise large-span flat roof. Wind tunnel tests were conducted to investigate the control effect of PVGs, and parametric analysis was performed, with parameters including the height, length, opening angle, tilt angle and interval of PVGs. The maximum reduction of peak wind pressure under the worst wind incident angle with PVGs reaches 74%, and they show excellent control effects at all wind incident angles. The recommended parameters of PVGs are also provided for engineering practice. Spectrum analysis and the structure of the conical vortices show that the streamwise vortices generated by PVGs which mixed into the conical vortices and can distort or destroy the conical vortices, and then alter the position of conical vortices axis and reduce the reattachment range. Meanwhile, the high frequency fluctuation is increased and the low frequency fluctuation is reduced accordingly.