Flow-Induced Transverse Vibration of a Cantilevered Prism for Energy Harvesting

Abstract

Various types of hydroelectric power generators have been developed, and small-scale hydroelectric power generation is expected to provide an independent, dispersed power supply for harnessing hydro-energy of small-sized rivers and agricultural waterways. In order to investigate the effects of the geometric shape of a bluff body’s cross section on the flow-induced transverse-galloping vibration, we performed free-vibration tests of a cantilevered prism with three kinds of cross sections, i.e., rectangular, D-section, and triangular prisms. The effects of the side ratio D/H (where D: depth of a bluff body in the flow direction, H: height of a bluff body normal to the flow direction) and the turbulence intensity of the free stream on the flow-induced vibration were also investigated. It was found that the vibrations of the thin rectangular, D-section, and triangular prisms occur at lower reduced velocity than that of the thick prisms. We also carried out a power-generation experiment using iron-gallium alloy that is a kind of magnetostrictive material to investigate a possibility of harvesting energy from the transverse-galloping vibration in a water flow. The energy harvester using magnetostrictive material and a rectangular prism with D/H = 0.2 generated a maximum electric power of 0.35 W at a reduced velocity of Vr = 4.4.