Interaction Between Vortex-Induced Vibrations and Base Vibrations in Piezoelectric Harvesters

In the present era, powering sensors using green energy is a significant challenge. One promising solution for the power supply of small sensors relies on piezoelectric energy harvesters excited by vortex-induced vibrations (VIVs) generated by wind. In these devices, the harvester typically features a cylindrical bluff body that generates the vortex shedding and also tunes the natural frequency of the cantilever according to the frequency of the excitation. However, in many practical applications, the harvester is not mounted on a perfectly rigid base. The compliance of the base can significantly influence the behavior of the system. Furthermore, harvesters are often installed on moving structures or machines, where base vibrations introduce additional complexities. Therefore, understanding the impact of both harmonic and random base excitations on VIV is essential for harvester design. This paper investigates these phenomena in a comprehensive way. It presents a multiphysics mathematical model of a piezoelectric energy harvester mounted on a moving base, numerical results, and a wide series of experimental tests. The model reliably predicts the harvester behavior under various conditions and enables to extend the experimental investigation. Experimental and numerical results show that base vibrations and VIV can generate voltage in a synergistic way. Nevertheless, for large base vibrations, nonlinear effects take place that affect the maximum amplitude of the generated voltage in the lock-in region. The study shows that these phenomena happen with both harmonic and random base excitation.