Experimental study of the flow-induced vibration of a cut-corner prism energy harvester

In this paper, an experimental study of the performance of the energy harvester was conducted to investigate the effect of the length of the parallel side (PS) on the cut-corner prism. The experiments were carried out in a recirculating wind tunnel within a range of Reynolds numbers from 2284 to 8893, based on the edge length D of the prism, and the range of cut-corner length was PS = 0.2D-0.8D. The experimental results show that the peak vibration amplitude of the prism initially rises and then gradually declines with increasing PS. Particularly, the maximum amplitude observed at PS = 0.5D is improved by approximately 1.9 times compared to that of the square prism. Within the wind speed range investigated, the cut-corner prism experiences three vibration modes: initial branch of vortex-induced vibration, transition, and galloping. The cut-corner prism will cause the vibrations to reach the galloping mode earlier compared to the square prism. As the vibration modes transition, the wake flow structures gradually shift from a 2S shedding mode, where two single vortices are shed per vibration cycle, to a 2P shedding mode, characterized by the shedding of two pairs of vortices per vibration cycle. For a finite-length prism, the phenomenon of shedding vortex splitting is observed due to the upwash and downwash flows. Before PS surpasses a critical value, the lateral side reattachment phenomenon vanishes with increasing PS length, leading to a decrease in shear layer curvature and separating bubble size, while enhancing negative pressure strength. However, exceeding the critical PS value allows shear layer reattachment, reducing amplitude. This explains why the effect of PS length on the efficiency of the prism energy harvester is non-monotonic.