Breaking Down of Rooftop Vortices with Nature-inspired Parapets over a Low-rise Building

The increasing frequency of severe wind events poses a growing threat, leading to significant fatalities and economic losses each year in the United States. Among the affected civil structures, low-rise buildings are particularly vulnerable. Wind-induced damage typically initiates at the windward roof corners and edges, where peak suctions are generated due to flow separation and the formation of conical vortices. This work focuses on the use of nature-inspired porous fractal parapets to reduce rooftop suction pressures at high Reynolds numbers. A series of wind tunnel experiments were conducted at Florida International University's Wall of Wind facility, involving flow and pressure measurements for four test cases: a bare roof (baseline), a fractal parapet, and two porous parapets with different strut thicknesses. Parapets were tested on a 1:6 scale model of a low-rise building, with a Reynolds number of approximately one million. The results show that the fractal parapets effectively break down the conical vortices responsible for the strongest suctions over a bare roof. As a result, peak suction pressures were reduced by up to 90% at a 45° wind angle compared to the baseline case.