Abstract
When the VIVACE converter is operated in shallow water, the free surface in its proximity plays a critical role in affecting the dynamic response and the consequent energy harvesting performance of the converter. In this study, a series of experimental tests are conducted for the flow-induced vibration of a single-cylinder VIVACE converter in the TrSL3 regime with the Reynolds number 34,931<Re<116,370 close to a free surface to examine this effect. The cylinder is placed beneath the free surface with a gap of 3.0D where D is the cylinder diameter and free to vibrate in the transverse direction only. The virtual damper–spring system is adopted to provide the damping and restoring forces. The values of the harnessing damping ratio considered are ζharness=0.04, 0.08, 0.12, 0.16 and 0.20 and the spring stiffness ranges from 600 to 1200 N/m. The amplitude response, frequency response, harnessed power and energy harnessing efficiency are investigated. When the VIVACE converter is in the vicinity of the free surface, the vortex-induced vibration (VIV) is initiated at a lower reduced velocity. Both the VIV and galloping regions are enlarged with a smoother transition between the two regimes. The harnessed power Pharness in the VIV region is slightly lower while higher Pharness is found in the galloping region. The efficiency of the cylinder near the free surface is lower in the VIV region and analogous to that in the deep submerged case when the cylinder is undergoing galloping. For a VIVACE converter placed near the free surface, its flow-induced vibration (FIV) and energy conversion features vary similarly with the damping and stiffness parameters to the far away from the free surface configuration. Overall, given that the governing parameters are carefully selected, it is viable to use the VIVACE converter close to the free surface for harnessing the hydrokinetic energy efficiently.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call