Development of the optimal bluff body for wind energy harvesting using the synergetic effect of coupled vortex induced vibration and galloping phenomena

Abstract

This study mainly focuses on the development of a bluff body for an efficient wind energy harvesting through the combination of two typical flow-induced motions: Vortex-induced vibration (VIV), and galloping. We investigated, both theoretically and experimentally, the possibility of the synergetic effect of coupled VIV and galloping motions based on two types of widely applied cross-sectional shapes of a bluff body (circular and square cylinder). A series of D cross-sectional cylinders were designed and fabricated with varying cutting angles and afterbody lengths, and their dynamic responses were investigated over a practical wind speed range. A newly-designed bulb cross-sectional cylinder (15 × 10 bulb cylinder) is proposed as an optimally-shaped bluff body, which can maximize the synergetic effect of VIV and galloping through the dynamic coupling of these two phenomena. The proposed bluff body is then applied to a wind-based vibratory energy harvester (WBVEH) that uses a piezoelectric energy conversion mechanism, leading to a significant average power increase of 75% over the entire wind speed range of concern and a maximum power lift rate of 193% at a wind speed of approximately 2.95 m/s, compared to the reference square cross-sectional bluff body.