Improving FIV energy harvesting characteristics using rigidly coupled cylinders

Rigidly coupled cylinders have become a research hotspot, and in the past, more attention was paid to its inhibition effect on vortex-induced vibration (VIV), ignoring its vibration harvesting energy performance. In this study, a system consisting of rigidly coupled cylinders with unequal diameters was designed. Numerical simulations, performed at low Reynolds number Re = 150, were used to examine the effects of flow orientation, diameter ratio (d0/D = 0.2, 0.4, 0.6, 0.8, 1.0), and reduced velocity Ur on vibration response, hydrodynamic behavior, vortex shedding patterns, and energy harvesting efficiency of the coupled system. The results reveal that, in the parallel configuration, the flow field exhibits increased complexity, leading to a significant enhancement of VIV compared to that of an isolated cylinder. In contrast, in the tandem configuration, VIV behavior is suppressed due to the shielding effect. Furthermore, within the experimental damping range, energy harvesting efficiency increases with higher damping ratios, reaching an optimal efficiency of 0.101 at a damping ratio of 0.1, representing a 546.49 % improvement over the efficiency at a damping ratio of 0.007. These findings position the proposed strategy as a promising alternative for enhancing the energy harvesting efficiency of VIV in low flows.