An omnidirectional piezoelectric energy harvester coupling vortex-induced vibration and wake galloping

This paper proposes an omnidirectional piezoelectric energy harvester coupling vortex-induced vibration and wake galloping (OPEH-VW), converting wind energy into electrical energy. The vibration behavior of the OPEH-VW is explored by changing the spacing ratio (L/D) and the diameter of the wind cylinder at the end of the cantilever beam. When the wind does not blow directly onto the device, it will rotate due to the imbalance of forces on both sides of wind cylinder B until reaching a state of equilibrium, causing the device to stop rotating, achieving omnidirectional functionality. And at this state, the efficiency of wind energy collection is highest. The results show that when the two wind cylinders of the same diameter were placed in series, at low wind speeds, vortex-induced vibration (VIV) was observed. As wind speed increases, continuous VIV and wake galloping (WG) phenomena appeared at a spacing ratio of 3.5, while only WG was occurred at the other three spacing ratios. And if the two wind cylinders placed in series replaced to different diameters, the OPEH-VW behaved as a bi-stable system with two resonance frequencies. The output power increased with the wind speed within a certain range and raised to peaks twice.