Dual-stage wind energy harvester utilizing synergy between two wake-galloping mechanisms and their internal resonance phenomena

This study introduces a high-efficiency dual-stage wind energy harvester to overcome the power-output saturation commonly encountered in conventional galloping-based harvesters at medium-to-high wind velocities. The system combines wake-interference galloping and wake-induced galloping with a 1:3 internal resonance between the upstream and downstream oscillators, thereby enhancing aeroelastic coupling and energy transfer. Piezoelectric and electromagnetic transducers are integrated into the two oscillators to harvest low-frequency and high-frequency vibration energy, respectively. Systematic modeling, simulations, and experiments were conducted to optimize the configuration and evaluate the harvesting performance. Additionally, a finite-time Lyapunov exponent analysis was performed to assess the wake evolution and clarify the relationship between the system's aerodynamic coupling and its stage-dependent dynamic response. A two-way fluid–structure–electrical interaction simulation framework was also developed for the two-degree-of-freedom harvester, with close agreement observed between the numerical predictions and the experimental measurements. Under the optimal configuration, the proposed harvester achieved an average output power of 19.24 mW at 10 m/s, demonstrating clear advantages over representative conventional galloping-based harvesters. Moreover, an application-oriented energy management scheme was developed, which underlines the practical potential of the proposed system.