Effects of unsteady stream on hydrodynamic behavior of flexible hydrofoil in semi-passive mode

Yubing Zhang, Qixian Wang, Jiazhen Han and Yudong Xie

Renewable Energy, 2023, vol. 206, issue C, 451-465

Abstract: The effects of unsteady stream on the hydrodynamic behavior of a flexible hydrofoil in the semi-passive mode are investigated in this study with the goal of improving power extraction. Specifically, the influences of flow velocity amplitude (λ), the frequency ratio (σ) between hydrofoil and flow velocity, and phase difference (ε) between the flow velocity and pitching motion of the hydrofoil are examined. The results reveal that σ has a significant effect on lift force and heaving velocity, thus severely affecting the average power coefficient (CP‾) and heaving response. The peak value of CP‾ is attained when σ = 2; this is attributed to the satisfactory synchronization between the flow velocity and heaving motion of the hydrofoil. Initially, CP‾ increases with ε until ε = 90°; then, it decreases as ε further increases. The equilibrium position of the heaving response is sensitive to both ε and λ. The relative relationship between the flow velocity and pitching motion is modified by ε, altering the evolution of the lift force, heaving velocity, vortex, and pressure distribution. Through comprehensive adjusting σ and ε according to λ, the hydrofoil encounters minimum incoming flow near the dead point. This is the key to improve power extraction.

Keywords: Oscillating hydrofoil; Flexible hydrofoil; Unsteady stream; Energy extraction; Semi-passive (search for similar items in EconPapers)
Date: 2023
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Citations: View citations in EconPapers (1)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:206:y:2023:i:c:p:451-465

DOI: 10.1016/j.renene.2023.02.071

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