Abstract

Extracting mechanical energy from flow-induced vibration (FIV) of cylindrical structures has become a critical research subject. In this paper, we numerically investigate the FIV of a D-section prism with various angles of attack (α) and look into energy harness from the identified multiple FIV responses by using immersed boundary method (IBM). We found that as α increases, six distinct responses appear. At α = 0°–40°, typical vortex-induced vibration (VIV) occurs where the amplitude first increases and then decreases with reduced velocity, showing similar behaviour to that of VIV of a circular cylinder. At α = 50°–60°, the vibration amplitude becomes larger, with a third branch observed. At α = 70° and 165°–180°, galloping response dominates where the amplitude generally increases with increasing reduced velocity. At α = 80°, a combined VIV and galloping response occurs. At α = 90°–145°, a narrowed VIV is observed where large-amplitude vibration exists in a narrowed reduced velocity range. At α = 155°–160°, the response behaves like a transition from narrowed VIV to galloping. Examinations of the energy harness from these identified responses indicate that in the VIV, energy extraction, including harness power (Ph) and efficiency (ηh), shows a strong dependence on the amplitude, while in the galloping, its dependence on the amplitude becomes significantly weak.

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