Numerical Analysis and Experiment of an Underwater Magnetic Nonlinear Energy Harvester Based on Vortex-Induced Vibration

Abstract

This paper designs an underwater magnetic nonlinear piezoelectric energy harvester (PEH) based on the principle of vortex-induced vibration (VIV). The magnetic force between the permanent magnets provides the basis for the system frequency modulation. According to the positional relationship between the PEH’s vibrator and the magnet, the values of the linear stiffness coefficient and the nonlinear stiffness coefficient can be determined. According to the value of linear stiffness coefficient, the system can be divided into hard stiffness system, soft stiffness system, and negative stiffness system. The results show that the hard stiffness system’s open-circuit voltage (VRMS) increases from 9.43 V to 10.31 V, and the frequency band is widened by up to 36.8%. According to the simulation and experimental data, the hard stiffness system has a better output effect in a high flow rate. For a soft stiffness system, its initial vibration velocity decrease. When the water flow velocity is 0.2 m/s, the output voltage of the nonlinear PEH from experimental data is 10 times that of the non-magnetic PEH. Both numerical simulations and experiments prove that the soft stiffness system is more suitable for application in a low-speed water environment.