Modeling and experimental study of a piezoelectric energy harvester from vortex shedding-induced vibration

Piezoelectric energy harvesters (PEHs) from fluid energy sources, particularly vortex shedding-induced vibrations, have received considerable attention in recent years. However, there still exists a common problem with these harvesters: the current optimum position of a vortex shedding-induced PEH located in the wake of a bluff body is commonly obtained through a series of experiments. This study proposes a theoretical model to determine the best position and demonstrate this mechanism. This theoretical model, which consists of fluid-structure and electromechanical couplings, is derived from the proposed PEH with a flapping sheet structure. The equivalent harmonic force in the fluid-structure coupling part caused by the vortexes on the flapping sheet is expressed by Bernoulli's law and Lamb-Oseen vortex model. The system equations in the electro-mechanical coupling part are then obtained utilizing Euler-Bernoulli beam theory and an equivalent circuit model. This model was validated initially through the published data in the reference and then through the experimental results from a proposed PEH prototype. The optimum position of the PEH in the flow field is revealed by the analytical solution in numerical results and examined in experimental results. Moreover, the balanced match of fluid velocity and bluff body diameter can also contribute to the high-level system performance under the optimal load resistance.