Improving piezoelectric wind energy harvesting performance with snowflake-shaped bluff bodies

Inspired by the morphology of Koch snowflakes, this study proposes a series of bluff bodies to enhance the performance of piezoelectric wind energy harvester (PWEH). Four snow-shaped sectional bluff bodies are designed: pentagon, hexagon, heptagon, and octagon. A distributed model is developed based on the extended Hamilton's for evaluating the dynamic response. Numerical simulation and wind tunnel experiments are conducted for verifying the theoretical model. The effect of inertial and windward angles: the Apex (denoted as A) and the Bident (denoted as B) are examined. Theoretical modeling, wind tunnel experiments, and three-dimensional (3D) vortex simulations are conducted to understand the dynamic response and reveal the underlying physical mechanisms. The experimental results indicate that the lock-in region was extended by 66.67 % for Pent (A) and by 33.33 % for Hept (B) compared with the cylinder. Additionally, the Am-Hex (A), Hex (A), Am-Hept (A), Hept (A), Am-Oct (B), and Oct (B) facilitate a transition from vortex-induced vibration (VIV) to galloping. Furthermore, the maximum power densities of wind energy harvesters with Pent (A), Hex (A), and Hept (B) surpass those with the cylinder by 257.93 %, 406.47 %, and 81.28 %, respectively. Three-dimensional computational fluid dynamics (3D-CFD) is used to analyze fluid-structure interaction mechanism of various snowflake-shaped bluff bodies. It is shown that different snowflake-shaped bluff bodies could affect the flow field characteristics and aerodynamic layout. Additionally, the capability of PWEH with a snowflake-shaped bluff to provide power for low-power electronics has been demonstrated through application testing.