Exploiting internal resonance to improve flow energy harvesting from vortex-induced vibrations

Abstract

Vortex-induced vibrations have been recently employed to capture scalable flow energy harvesters, which can attain the maximum power when the wind speed is in the lock-in region where the vortex-shedding frequency is close to the structural frequency. Nevertheless, the dynamical mechanism of the synchronization phenomenon has not been reported. To solve this critical problem, in this paper we explore a novel internal resonance to scavenge flow energy from vortex-induced vibrations, the mechanism of synchronous oscillations is introduced by the amplitude-frequency relationship and confirmed by the energy function. To show the capturing performance, an electromagnetic energy harvester with one-to-one internal resonance is proposed. Based on the harmonic balance method, the electromechanical coupling equations are decoupled, and the first order approximate harmonic responses of displacement and current are established. The modulation equations are derived, the amplitude-frequency curves of displacement and current are plotted with different detuning parameters. The advantage of the proposed one-to-one internal resonance is compared to the noninternal resonance case, the results express that the internal resonance scheme can enhance flow energy capture. The effects of physical parameters on the scavenged power are discussed. The accuracy and efficiency of the approximate analytical results are checked by numerical simulations.