Nonlinear dynamics of a quasizero energy harvester forced by flow and kinematic excitations

The paper proposes a novel design of a high-efficiency nonlinear energy harvester that benefits from the synergy between a quasi-zero stiffness system and flow-induced excitations. We demonstrate that this innovative approach enables improved adaptability and energy output. The harvester consists of a cantilever beam in a flag-like configuration subjected to both air-flow and kinematic excitations. In the wake galloping scenario, the variable lift force generated behind a fixed bluff body interacts with the tail-like cantilever beam. Using finite element modeling, we identified the lift force across a wide spectrum of air velocities and incorporated it as an excitation in a dimensionless mathematical model. Subsequently, vibrations of the cantilever beam, leading to the generation of electromotive force in an attached piezoelectric element. The system's displacement and voltage output responses were analyzed using nonlinear dynamics tools. An important advantage of this design is its tunability – by adjusting the elastic elements, the potential function can be configured for optimal performance. Key findings also concern the behavior of the system in chaotic and periodic motion zones and their impact on efficiency. We used tools such as the Lyapunov exponent, bifurcation diagrams, and Poincare sections to analyze nonlinear dynamics. We also identified transient chaos and periodic, chaotic, and quasi-periodic solutions to determine their impact on the performance of the system. The study further explores coexisting solutions and evaluates the effectiveness of the system under different types of excitation, both individually and together. The results demonstrate that the harvester maintains high efficiency even at low excitation levels, highlighting its potential for practical applications.