Enhancing piezoelectric energy harvesting from the flow-induced vibration of an apple-shaped bluff body based on topology optimization

This study introduces an apple-shaped bluff body for wind energy harvesting, developed through topology optimization, to significantly enhance energy conversion efficiency by coupling vortex-induced vibrations and galloping. Compared with traditional shapes, the apple-shaped design features complex flow patterns of separation and reattachment, resulting in higher oscillation amplitudes and lower cut-in wind speeds. Prototypes with different stalk cavity angles (α) were tested. Wind tunnel experiments indicated that the apple-shaped structure (α = 80°) performed best at lower wind speeds (1.5–3.6 m/s). At higher wind speeds (3.6–5.0 m/s), the configuration with the angle of α = 120° was more advantageous for increasing voltage output. Additionally, adjusting the distance (L) between two stalk cavities of the apple-shaped structures (α = 80° and 120°) significantly affected the energy harvesting performance. The experimental results indicate that the most effective energy harvesting was achieved at L = 35 mm. Compared to a square prism, the apple-shaped structure (α = 120°, L = 35 mm) showed an 85 % increase in maximum voltage output. Computational fluid dynamics simulations validated the coupled vortex-induced vibration and galloping phenomena and superior energy harvesting performance of the apple-shaped bluff body. This study provides valuable insights into the design of efficient piezoelectric energy harvesters using topology optimization techniques.