Abstract
Flow-induced motion (FIM) performs well in energy conversion but has been barely investigated, particularly for prisms with sharp sections. Previous studies have proven that T-section prisms that undergo galloping branches with high amplitude are beneficial to energy conversions. The FIM experimental setup designed by Tianjin University (TJU) was improved to conduct a series of FIM responses and energy conversion tests on a T-section prism. Experimental results are presented and discussed, to reveal the complete FIM responses and power generation characteristics of the T-section prism under different load resistances and section aspect ratios. The main findings are summarized as follows. (1) Hard galloping (HG), soft galloping (SG), and critical galloping (CG) can be observed by varying load resistances. When the load resistances are low, HG occurs; otherwise, SG occurs. (2) In the galloping branch, the highest amplitude and the most stable oscillation cause high-quality electrical energy production by the generator. Therefore, the galloping branch is the best branch for harvesting energy. (3) In the galloping branch, as the load resistances decrease, the active power continually increases until the prism is suppressed from galloping to a vortex-induced vibration (VIV) lower branch with a maximum active power Pharn of 21.23 W and a maximum ηout of 20.2%. (4) Different section aspect ratios (α) can significantly influence the FIM responses and energy conversions of the T-section prism. For small aspect ratios, galloping is hardly observed in the complete responses, but the power generation efficiency (ηout,0.8 = 27.44%) becomes larger in the galloping branch.
Highlights
The flow-induced motion (FIM) phenomenon [1] widely exists in the civil engineering field, and it can lead to the failure of oscillating structures such as solar receiver tubes [2,3,4], long-span bridges [5], parallel twin bridges [6], offshore risers [7], and aircraft [8]
(3) In the galloping branch, as the load resistances decrease, the active power continually increases until the prism is suppressed from galloping to a vortex-induced vibration (VIV) lower branch with a maximum active power Pharn of 21.23 W and a maximum η out of 20.2%. (4) Different section aspect ratios (α) can significantly influence the FIM responses and energy conversions of the T-section prism
The specific findings are listed as follows: (1) With an increase of damping, the T-section prism oscillation mode gradually changes from soft galloping (SG) (0.115 ≤ ζ ≤ 0.165, 18 Ω ≤ RL ≤ 51 Ω) to critical galloping (CG) (ζ = 0.177, RL = 16 Ω), and eventually to Hard galloping (HG) (0.208 ≤ ζ ≤ 0.305, 8 Ω ≤ RL ≤ 13 Ω)
Summary
The flow-induced motion (FIM) phenomenon [1] widely exists in the civil engineering field, and it can lead to the failure of oscillating structures such as solar receiver tubes [2,3,4], long-span bridges [5], parallel twin bridges [6], offshore risers [7], and aircraft [8]. Many creative structures [18,19,20] have been proposed for exploiting this energy, especially for the vortex-induced vibration (VIV) [21] and galloping [22,23] responses of FIM. VIV occurs due to the alternating shedding of vortices from either side of the bluff cylinder [1]. An isolated smooth circular cylinder can only undergo VIV, while galloping is rarely observed [25]. On the contrary, galloping is observed for non-circular-section prisms such as rectangular prisms, triangular prisms, and passive turbulence control (PTC) circular cylinders, etc
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