Magnet-induced monostable nonlinearity for improving the VIV-galloping-coupled wind energy harvesting using combined cross-sectioned bluff body

This study proposes a novel wind energy harvester that exploits both vortex-induced vibration (VIV) and galloping phenomena with a hybrid cross-sectioned bluff body. Magnetic-induced monostable nonlinearity is then introduced in the harvester to improve its energy harvesting performance. The bluff-body cross section uses the combination of 3/4 round and 1/4 square to introduce the coupled VIV and galloping, and the magnetic repulsive force of the two magnets is employed to realize the monostable nonlinearity. Governing equations bringing together the VIV, galloping and magnet-induced monostable nonlinearity are established. Wind tunnel experiment is first conducted to validate the aerodynamic model of the governing equations without the monostable nonlinearity, which reveals the advantage of the coupled VIV and galloping for performance improvement. Consequently, the numerical simulations are performed to reveal the benefit of the magnet-induced monostable nonlinearity for wind energy harvesting. Results show that compared to the coupled VIV-galloping harvester without the monostable nonlinearity, the proposed monostable harvester can reduce the cut-in speed of galloping, which boosts the voltage output in a wider wind speed range and further promotes the advantages of the combination of VIV and galloping.