Boosting energy harvesting efficiency from wake-induced vibration using a multi-cylinder configuration

Marine current energy harnessed through vortex-induced vibration (VIV) offers a cost-effective solution for renewable energy generation, particularly in low-velocity flow environments. This study proposes a novel approach to enhance VIV energy harvesting efficiency by employing a multiple-cylinder configuration with a passive vortex generator, where the optimized diameter and spacing ratios of the fixed upstream cylinder are considered to enhance the vibration response of the cylinders positioned downstream. Initially, we analyze the impact of spacing ratios on the vibrations of the downstream tandem cylinders and identify the optimal spacing ratio. Subsequently, we explore the influence of damping ratios on the energy harvesting efficiency for the oscillating tandem cylinders. Through detailed examinations of the cylinders’ responses and forces in both frequency and time domains, we elucidate the strong interference between wakes and its impact on system dynamics. Our results demonstrate significant improvements in vibration amplitudes and energy efficiency for spacing ratios ranging from 5 to 20, with an optimal spacing ratio of 7 identified. Despite an increase in damping resulting in decreased vibration amplitudes, energy harvesting remains high for damping ratios larger than 0.2. The highest accumulated energy capture is observed at a damping ratio of 0.35 for the considered reduced velocity range of 3 to 13. Our findings suggest that VIV harvesters perform better in tandem configurations than a single cylinder configuration, offering a promising alternative for boosting energy harvesting efficiency from wake-induced vibration (WIV) in low-velocity water flows.