Experimental investigation on hydrokinetic energy harvesting from flow-induced vibration of oscillators with rod-shaped attachments

The vibrational characteristics and generating capacity of a column oscillator are significantly influenced by its cross-sectional shape, as widely acknowledged. However, the impact of attachments on enhancing the generating capacity of oscillators remains uncertain. Therefore, this study aims to investigate, the vibration characteristics and generating capabilities of an elastically supported oscillator with semicircular attachments specifically designed for low-speed seafloor current environments. Experimental tests were conducted at zero degrees incidence under the turbulent wake conditions with Reynolds numbers ranging from 5.041 x 103 to 7.562 x 104. The hydrodynamic properties of the oscillators were evaluated using statistical analysis, Proper Orthogonal Decomposition (POD), and vortex core identification based on Particle Image Velocimetry (PIV) fields. Furthermore, the generating capability of the oscillator was assessed through statistical analysis considering its vibration displacement, frequency, and amplitude measurements. The results indicate that an oscillator with symmetric sharp attachments and without vortex reattachment is favorable for self-excitation vibration. An oscillator equipped with 0.2D semicircular rod-shaped attachments arranged at an angle of 60 degrees demonstrates superior generating capacity, achieving a peak efficiency of 22.3% at Ur = 9.1. These experimental findings provide valuable optimization solutions for harnessing power from flow-induced motion.