On the energy harvesting potential of an airfoil-based piezoaeroelastic harvester from coupled pitch-plunge-leadlag vibrations

Aeroelastic energy harvesters are designed to generate electric power from the aeroelastic vibrational energy. Several designs are based on the flutter of pitch-plunge airfoils with piezoelectric transducers coupled to the plunge degree of freedom. In this paper, inspired by the coupled pitch-plunge-leadlag aeroelastic vibrations of rotor blades and slender wings, an airfoil-based piezoaeroelastic energy harvester is proposed with an additional supporting device (including flexural springs and piezoelectric transducers) corresponding to the leadlag degree of freedom. The dynamic model of this harvester is derived considering the coupling between the leadlag motion and the pitch-plunge motion and the inertia nonlinearity due to the large-pitch-amplitude vibrations. The aerodynamics is obtained based on the ONERA dynamic stall model. The average power output is calculated to evaluate the energy harvesting performance. It is found that the power output from the leadlag motion is much smaller than that from the plunge motion with the same supporting devices, but the gap is narrowed with increasing flow velocity. Beyond a critical flow velocity corresponding to the occurrence of the dynamic stall, the power output from the leadlag motion increases sharply. The effects of the load resistances, the torsional stiffness nonlinearity, the airfoil mass eccentricity, the mass of the supporting devices, and the airfoil mass moment of inertia are numerically studied, respectively. The results show that an optimal resistance in each external circuit is found for the power output from the corresponding degree of freedom. Besides, the nonlinear torsional stiffness and the airfoil mass eccentricity, respectively, can be tuned to maximize the power outputs from the plunge or leadlag motion. Generally, as dynamic stall occurs, the varying of the power outputs with the investigated parameters become complicated with fluctuations or even opposite variations. This may result from the coupled inertia, stiffness, and aerodynamic nonlinearities.