Piezoelectric Cantilever Bluff Body Energy Harvesting by Vortex-Induced Vibration in a Low-Speed Open Wind Tunnel

This study presents research on wind-induced vibration energy harvesting (WIVEH) systems, focusing on those consisting of a flexible beam with piezoelectric transducers (PZT) coupled with bluff-body geometries in a low-speed open wind tunnel. Three configurations were examined: a single-cylinder, two-cylinders connected by a flat wall, and a cylinder-cuboid hybrid. Continuous wavelets transform (CWT) analysis and statistical evaluation of beam deflections were employed to assess vibration characteristics, frequency content, and voltage output across air velocities from 3.5 to 15 m/s. Physical experiments are performed to compare the performance of systems with different configurations of bluff-body shape. Investigation demonstrates the role of nonlinear aerodynamic excitation mechanisms of the vortex-induced vibrations (VIV), galloping, and fluttering effects. The paper discusses the influence of design parameters and challenges in modelling complex fluid-structure interactions with piezoelectric materials. Results show that bluff body geometry strongly influences beam vibration amplitude, frequency content, and energy harvesting efficiency. The two-cylinders configuration exhibited the highest vibration amplitudes, with an 89%, and maximum energy output (~140 μW), increase in variability relative to the single-cylinder, but at the cost of excessive oscillations beyond 10 m/s, compromising structural stability. The single-cylinder configuration showed moderate and predictable behavior with exponential voltage growth (~110 μW), while the cylinder–cuboid hybrid achieved the most robust performance, with 15% lower variability growth compared to the single-cylinder and stable operation above 15 m/s. These findings confirm that geometry-driven flow–structure interactions determine the balance between harvested power and operational safety. The results indicate that while two-cylinder configurations may be effective for controlled low-speed applications such as heating, ventilation, and air conditioning (HVAC) ducts, the cylinder-cuboid hybrid is better suited for broadband, variable-speed environments powering Internet of Things (IoT) devices and wireless sensors.