Investigation of flow-induced vibration and energy extraction of a bluff body with different immersed depths and cross section shapes

This paper investigated the effects of immersed depth and cross section shape on flow-induced vibration (FIV) response and power harvesting performance by experiment and numerical simulation. The experiment was carried out in a recirculating water channel. Three cross section shapes were considered: circular, square, and equilateral triangle. The reduced velocity spans from 3 to 15. The range of immersed depth ratio H* = Hi/D is from 2 to 8, where Hi is the immersed depth, D is the reference length of the cylinders, and the case of H* = 8 is fully immersed in water. The results show that vortex-induced vibration response in the crossflow direction of a circular cylinder is observed when the immersed depth ratio reaches H* ≥ 6. Out of the cylinders examined, the triangular cylinder exhibits the strongest amplitude response. The maximum amplitude in the crossflow direction of the triangular cylinder, reaching 2.38D, is obtained at H* = 8 and U* = 15. The energy output performance of the FIV energy harvesting system is the most superior when utilizing triangular cylinders. Importantly, when the triangular cylinder is completely immersed in water and the reduced velocity surpasses 10, it has the capability to produce an output power that exceeds 1200 μW.