Performance enhancement of a galloping-based energy harvester with different groove depths on square bluff body

This paper focuses on the effects of a V-shaped groove depth on the performance of a galloping-based energy harvester. The study simulated air flow over cylindrical, square, and different depth grooved square bluff bodies using a computational fluid dynamics program with a user defined function added. An experiment using the particle-image velocimetry technique in a closed-loop wind tunnel was also conducted to validate and explain the results. The results show that the energy harvester and square bluff body with a ratio of 0.25 groove depth to the side generated the most power of 15.24 mW, which is 1.34 times higher than the power generated by the square bluff body at 9 m/s wind speed. This is because the groove on the windward side of the square bluff body increased the striking area of the fluid force and triggered the formation of a large vortex beside the bluff body. This results in a larger vibration amplitude and in an increased generation of electrical power. The discrepancy between the simulated and experimental results was also discovered to be due to a twist of the bluff body and hence a common used one-dimension oscillation assumption might be invalid.