Galloping energy harvesting has received great attention due to its simplicity in capturing flow energy. Shaping bluff bodies with different surface protrusions has been proven to obviously alter the amplitude and mode of oscillations, and only leeward protrusions can enhance the galloping vibration amplitude. This paper mainly focuses on determining the optimal lengths of rectangular, triangular, and elliptical leeward protrusions. An electromechanical mathematical model was established based on the extended Hamilton’s principle and Euler- Bernoulli beam theory to predict the dynamic responses of the galloping energy harvester. Based on the developed model and corresponding wind tunnel simulations using Computational Fluid Dynamics (CFD), it is shown that the optimal lengths of rectangular, triangular, and elliptical protrusions are 14 mm, 17 mm, and 17 mm, respectively. Further impedance matching simulations also reveal that the optimal load resistances for the different protruded bluff bodies are all around 300 kΩ, as long as the wind speed is greater than the galloping cut-in speed. Furthermore, the output power of the three optimally designed protruded bluff bodies outperforms that of the original bluff body by 118.94%, 178.07%, and 187.38%, respectively, at the wind speed of 5 m/s. This also indicates that elliptical surface protrusions have a great potential to enhance the galloping energy harvesting performance.
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