Dynamics and performance evaluation of wind-induced vibration of a cuboid bluff body with two ornaments

The geometric design of the bluff body has a decisive effect on the wind-induced vibration energy harvesting performance. Aiming to enhance the properties of the wind-induced vibration energy harvester at the low-speed wind, we presented a wind-induced vibration energy harvester with two symmetrical additional ornaments, and the effects of installation location and size of ornaments on a cuboid bluff body are comprehensively studied. A distributed parameter model is developed based on the Euler-Lagrange equation. Corresponding numerical simulation and wind tunnel tests are implemented to evaluate the dynamics and performance of wind-induced vibration. The results show that the wind-induced vibration energy harvesters with various bluff bodies may exhibit galloping or vortex-induced vibrations (VIV) based on the position of ornaments and h/D_B (h is the height of the ornament and D_B is the diameter of the cuboid bluff body. For both Square-Front-h/D_B (S–F-h/D_B) and Square-Middle-h/D_B (S-M-h/D_B), the aeroelastic energy harvesting performance and the root-mean-square output voltage (V_rms) are improved in the low-speed wind. Compared with the cuboid bluff body, the critical wind speed (the smallest wind speed for triggering vibration) of S-M-0.25 is reduced by 18.18%, and the maximum voltage output reaches 10.89 V, which is increased by 105.72%. Afterwards, the three-dimensional computational fluid dynamics (3D-CFD) studies are conducted by Xflow to investigate the inherent physical mechanism of performance improvement. The results of vorticity vectors and vorticity contours verify the experimental results and reveal the insight mechanism of aerodynamic change. This work could provide a theoretical basis for optimizing wind-induced vibration energy harvesters and improving the performance of aeroelastic energy harvesting.