# Dragonfly-Wing-Inspired Bluff-Body Piezoelectric Harvester for Efficient Low-Wind-Speed Energy Harvesting

## TL;DR

A dragonfly-inspired wind energy harvester improves efficiency at low wind speeds by optimizing wing-opening angles for better performance.

## Contribution

A novel bio-inspired bluff-body design for piezoelectric harvesters that enhances low-wind-speed energy harvesting efficiency.

## Key findings

- The α = 15° configuration outperforms others across the tested wind speed range.
- The cut-in wind speed is reduced to 1.7 m/s with significant increases in voltage and power output.
- CFD analysis shows that specific angles enable stable oscillations via coupled VIV and galloping.

## Abstract

Inspired by the wing-opening morphology of dragonflies, a series of bio-inspired dragonfly-shaped bluff bodies are designed and investigated, and further integrated into a piezoelectric wind energy harvester. The energy-harvesting performance and aerodynamic responses of bluff-body configurations with different wing-opening angles (0°, 15°, 30°, 45°, and 60°) are comparatively analyzed through a combination of numerical simulations and wind tunnel experiments. Experimental results demonstrate pronounced differences among the configurations in the low wind speed regime. Specifically, the prototype with α = 0° achieves relatively higher output under very low wind speeds, whereas the α = 15° configuration exhibits the best overall performance across the entire tested wind speed range. Taking the α = 15° case as an example, the cut-in wind speed is reduced to 1.7 m/s, while the maximum RMS voltage and output power are increased by 20.16% and 44.39% compared with the cuboid bluff body, and by 50.95% and 127.84% compared with the cylinder bluff body, respectively. Further CFD results reveal that, at specific wing-opening angles, the dragonfly-shaped bluff body undergoes a coupled vortex-induced vibration (VIV) and galloping response, enabling certain configurations to sustain stable oscillations with large amplitudes over a relatively wide wind speed range. Within the investigated parameter range, an appropriate selection of the wing-opening angle effectively balances the cut-in capability and output stability under low wind speed conditions. These findings provide useful design guidelines for flow-induced vibration-based wind energy harvesters operating in low wind speed environments.