Energy harvesting using an inverted piezohydroelastic flag with resistor–inductor–capacitor circuit

Abstract

We develop a high-fidelity multi-physics model and, by using it, study the energy conversion process of a piezohydroelastic flag. Instead of a regular flag with a clamped upstream leading edge, we use an inverted flag so as to make the best of fluid elastic instability for energy harvesting. Moreover, different from many previous studies where a resistor–capacitor (RC) circuit is usually used, we adopt a resistor–inductor–capacitor (RLC) circuit for electricity generation. The influences of several key parameters associated with fluid, structure and electric dynamics are studied. Significantly different response modes are identified, among which the symmetric- and asymmetric-flutter modes are most suitable for sustainable energy harvesting, both emerging with moderate bending stiffness. If only deploying the RC circuit, increasing the resistance makes the flag more stable. By adding an inductor to turn the RC circuit into an RLC one, we observe the occurrence of ‘lock-in’ between the flag frequency and the circuit frequency as first reported on a regular flag by Xia et al. (Phys. Rev. Appl., vol. 3, 2015, 014009). This phenomenon can significantly enhance the energy output, but it only happens when the circuit resistance is sufficiently large. From a derivation based on dynamic mode decomposition analysis, we further identify an optimal condition for maximizing the energy output, which can serve as a guideline to determine whether deploying an inductor can boost the performance, and, if yes, the required inductance. The findings from this study can better guide the design of flow-induced-vibration-based piezoelectric energy harvesters for microelectronic devices.