Design Feasibility of a Vortex Induced Vibration Based Hydro-Kinetic Energy Harvesting System

The vortex induced vibration (VIV) based power generating system discussed in this paper is a new concept in power generation from fluid flows in oceans, rivers and streams. The possibility of harnessing energy from the vibrations incurred in a bluff body due to the phenomenon known as VIV, in which motion is induced on a body facing an external flow due to the periodic irregularities in the flow caused by boundary layer separation is explored. The VIV system is based on the idea of maximizing rather than spoiling vortex shedding and exploiting rather than suppressing VIV. The vibrating bodies are in turn used to harness energy using an efficient power-take-off system. The study of fluid dynamics, along with maintaining vortex shedding over the synchronization range, plays an important role in the design of such a system. Apart from this, the main challenge in the design of a VIV generator is introducing optimal damping and low mass ratios for high energy conversion and an efficient power take- off mechanism. This work presents a scoping study of such a device. In contrast to previous work on forced vibrations, the present study focuses on free vibrations that arise due to the shedding of vortices from a cylinder. The working and design considerations of the energy converter is outlined starting with a set of basic definitions pertaining to this technology.