Abstract
We consider the effects of the aspect ratio L/H (where L is the length of a prism, and H is the height of a prism normal to the flow direction) and the size of additional structures (which are a plate and a fin on the surface of a prism) on a vibration characteristic of a cantilevered rectangular prism. The present research is intended to support the analysis of energy harvesting research on the flow-induced vibration in water flow using a magnetostrictive phenomenon. The prisms are constructed from stainless steel and mounted elastically to a plate spring attached to the ceiling wall of the water tunnel. The prisms with aspect ratios of L/H ≥ 5 have reasonably identical vibration characteristics. However, the difference in the vibration characteristic appears distinctly on a rectangular prism with an aspect ratio of L/H = 2.5. The rectangular prism with an aspect ratio of L/H = 10 and a side ratio of D/H = 0.2 has a stable and large response amplitude and oscillates with a lower velocity. The length of the added plate and the size of the added fin influence the velocity of vibration onset. If the length of the added plate and fin size on the rectangular prism with D/H = 0.2 becomes large, the curve of the response amplitude shifts to that of the rectangular prism with D/H= 0.5. The response amplitude of the rectangular prism with/without plate or fin is found to be related to the second moment of area of the prism.
Highlights
Key features of a two-dimensional prism with a rectangular cross-section in a uniform flow are the generation of alternating vortices behind the prism and the separation bubble on the side surfaces of the prism
We consider the effects of the aspect ratio L/H and the size of additional structures on a vibration characteristic of a cantilevered rectangular prism
The present research is intended to support the analysis of energy harvesting research on the flow-induced vibration in water flow using a magnetostrictive phenomenon
Summary
Key features of a two-dimensional prism with a rectangular cross-section in a uniform flow are the generation of alternating vortices behind the prism and the separation bubble on the side surfaces of the prism. Flow characteristics of fluid forces and vortex shedding frequency have been dramatically changed by the side ratio of rectangular prisms [1]. Because of these features, the elastically mounted rectangular prisms experience the flow-induced vibration in crossflow directions by vortex-induced and galloping vibrations [2] [3]. The near wake structure is dependent on the aspect ratio, L/H, of the prism, where L is the length of the prism and H is the height of the prism normal to the flow direction. Below the critical aspect ratio, the arch and tip vortices can be observed in the wake flow of a finite prism
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