This study investigates the performance of a double-beam piezo-magneto-elastic wind energy harvester (DBPME-WEH) when exhibiting a galloping-based energy harvesting regime under wind excitation. The DBPME-WEH comprises two piezoelectric beams, each of which supports a prism bluff body embedded with a magnet at the tip. The magnets are oriented to repulse each other to introduce a bistable nonlinearity. Wind tunnel tests were conducted to compare performances of the DBPME-WEH and a double-beam piezoelectric wind energy harvester (DBP-WEH) that does not comprise the magnet-induced nonlinearity. The results reveal that compared to the DBP-WEH, the critical wind speed to activate the galloping vibration of DBPME-WEH can be reduced up to 41.9%. Thus, the results corroborate the significant performance enhancement by the DBPME-WEH. It can also be found that the distance of the two magnets affects the performance and the distance that achieves the weakly bistable nonlinearity is beneficial to energy harvesting in reducing the critical wind speed and improving the output voltage.

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.

This study performs a comprehensive parametric study and optimization of a piezoelectric wind energy harvester subjected to the conjunction of vortex-induced vibration (VIV) and galloping. The mathematical model of the harvester undergoing both the VIV and galloping is formulated, which is experimentally validated through the wind tunnel tests. The experimental results uncover that different combinations of the aerodynamic parameters of the model significantly influence the system dynamic behaviors. Changing the bluff body’s cross-section shape can alter the aerodynamic parameters. In the experiment, a unique hump phenomenon due to the coupled VIV and galloping is discovered, which significantly improves the voltage output. The influence of each aerodynamic parameter on the system performance is revealed, and the aerodynamic parameter’s effect is also mathematically interpreted by the terms in the governing equations. Finally, this study presents an effective structural optimization method based on the genetic algorithm (GA) to seek the optimal structural natural frequency matching up the given aerodynamic parameters. Results show that the piezoelectric wind energy harvester with the optimal designed natural frequency outperforms the harvester with other values, and the performance is also robust against a certain range of the parametric uncertainties.