Energy harvesting performance of an elastically mounted semi-circular cylinder

Energy extraction from ocean or wind currents through flow-induced vibration (FIV) of cylindrical structures is an important means of generating clean and renewable energy in nature. In this paper, we focus on investigating the response and energy harvesting performance of a semi-circular cylinder subjected to low- and high-Re (Reynolds number) cross-flow. Irrespective of Re, we observe six different types of FIV responses within the angle of attack (α) range of 0°–180°. Based on the characteristics of the vibration amplitudes and frequencies, these responses are categorized as typical VIV, extended VIV, narrowed VIV, galloping, combined response, and transition response. To assess the energy harvesting performance of these responses, we analyze the harvested power (Ph) and efficiency (ηh). Our findings indicate that in the VIV regimes, Ph and ηh are strongly dependent on the amplitude. However, an exception is noticed in the third branch of the extended VIV, where the amplitude is significantly large but Ph and ηh are small. In the galloping regime, the dependence of Ph and ηh on the amplitude becomes weak. Amongst all the response regimes, the galloping at α = 180° exhibits the best energy harvesting performance, with the highest ηh reaching 46.5%. In the combined response, Ph and ηh are significantly small, regardless of whether it occurs in the VIV or galloping (or large-amplitude vibration) region. Further, we confirm the significant influences of the damping coefficient and mass ratio on the energy harvesting performance. By selecting the optimal damping coefficient and mass ratio, both Ph and ηh are significantly improved.