High performance energy harvesting from flow-induced vibrations in trapezoidal oscillators

Flow-induced vibrations (FIVs) are of great interest in various engineering fields. Although FIVs possibly cause some undesirable response and fatigue damage, they can also be used to harvest hydraulic and wind energy. This paper investigated the effects of the attack angle (α) and length ratio (d/D) of a trapezoidal oscillator on the FIV response and energy harvesting capability. The experimental results illustrate the occurrence of a full interaction between the vortex-induced vibration (VIV) and galloping at α = 0° and α = 90°. The attack angle and length ratio greatly influence the energy harvesting. In general, a trapezoidal oscillator at α = 0° exhibits better energy harvesting than that at α = 90°. At α = 0°, the triangular oscillator gains the maximum amplitude of 0.703D with an output voltage of 10.407 V, harvested power of 24.056 mW, and harvesting efficiency of 12.151%. Nevertheless, the performance is reduced as the length ratio increases. At α = 90°, a trapezoidal oscillator with d/D = 0.5 is considered as the best one for energy harvesting. The computational fluid dynamics (CFD) analysis indicates that the displacement is highly related to the transferred energy between the oscillator and the fluid. A greater amount of transferred energy is the main cause of larger displacement, resulting in a more disordered vortex shedding. Finally, it is recommended to install a triangular oscillator at α = 0° to deliver optimal energy harvesting.