Characteristics of flow-induced vibration of cut-corner prisms at different aspect ratios

This paper presents an experimental investigation of flow-induced vibration characteristics of cut-corner prisms with various aspect ratios (H* = 1.0-13.33). Experiments were conducted in a recirculating wind tunnel with Reynolds numbers ranging from 2651 to 7953, based on the prism's side length. Four prism types (square, PS = 0.2D, PS = 0.5D, and PS = 0.8D, where PS is the cut-corner length parallel to the incoming flow) exhibited five distinct vibration modes as wind speed increased: vortex-induced vibration (VIV), transition from VIV to galloping, pure galloping, separated weak VIV-like and galloping, and coupled VIV and galloping. Compared to the square prism, cut-corner prisms transition from VIV mode to galloping mode at higher aspect ratios. As H* increases, end effects diminish, resulting in more concentrated vortex shedding and the disappearance of vortex splitting. The vortex shedding mode transitions from 2S (two single vortices shed per vibration cycle) to 2 P (two pairs shed per vibration cycle). Additionally, the prism with the largest amplitude transitions from PS = 0.8D to PS = 0.5D. Unilateral close-view particle image velocimetry results show that as H* decreases, the shear layer is stretched away from the rear end of the prism due to end effects, altering the interaction between the shear layer and the prism and causing a transition between galloping and VIV modes. This study provides valuable insights for optimizing the design of cut-corner piezoelectric wind energy harvesters.