Enhancing performance of a spherical FIV piezoelectric energy harvester by tandem cube effects

The rapid expansion of the Internet of Things (IoTs) has intensified the demand for sustainable energy solutions to power decentralized sensing nodes. Flow-induced vibration (FIV) of spherical structures offers a promising approach for energy harvesting. However, enhancing their response bandwidth and power output remains a significant challenge. This study proposes a novel Spherical Flow-induced Vibration Piezoelectric Energy Harvester (SFVPEH), featuring a fixed upstream interference cube and a vibrating downstream sphere mounted coaxially. The performance of the SFVPEH was systematically evaluated through experimental characterization and Lattice Boltzmann Method (LBM) simulations. Experimental results demonstrate that the upstream cube achieves effective flow field modulation, leading to a robust lock-in effect and significantly enhanced output. Specifically, at L = 0.5D and s = 0.1D, the lock-in range expanded from 1.91–2.52 m/s to 1.75–3.67 m/s, representing a 315% increase in bandwidth. Under the optimal matching (s = 0.2D, L = 0.5D), the RMS voltage reached 23.38 V, a 284% improvement over the standalone sphere. LBM simulations further confirm that the enhanced performance stems from highly coherent 3D vortex structures induced by the interferer. Finally, the SFVPEH successfully powered a wireless sensing node, demonstrating its practical viability for battery-free IoTs applications. This research provides a high-efficiency strategy for FIV energy harvesting in complex fluid environments.