Investigation of the hydrodynamics and wake characteristics of a floating twin-rotor tidal stream turbine under surge motion with free surface consideration

Junhui Xu, Yuquan Zhang, Yuan Zheng, Yajing Gu and Emmanuel Fernandez-Rodriguez

Energy, 2025, vol. 320, issue C

Abstract: To exploit the tidal capacity at sites with high depths, it is necessary the development of unconventional concepts, such as floating turbines. In this paper, the hydrodynamic and wake interference characteristics of the floating twin-rotor turbine is investigated under demonstrative surge conditions: periods (3s, 6s, 9s) and amplitudes (0.3D, 0.2D, 0.1D). Based on the overlap grid technique, simulations combine the rotation and surge motion of the twin rotors and consider the free surface condition. The results demonstrate that the hydrodynamic load of the twin rotors fluctuates periodically with frequency equal to the surge's, owing to the selected lateral spacing among turbines (1.5D). However, the surge amplitude and frequency augments the instability of the individual wakes, promoting their collision and momentum energy exchange with the free-stream flow. For instance, the spiral-shaped tip vortex of the turbine compresses to form a vortex ring but then collides and breaks into a group of small-scale vortices. Finally, the evolution of the vertical vorticity is dominated by the stretching term, defined in the enstrophy transport equation. Although findings are limited to one degree of motion, they may provide guidance for the selection of the floating platform as to reduce the fatigue loads on the turbine.

Keywords: Twin-rotor floating tidal turbine; Wake characteristics; Hydrodynamics; Surge motion; CFD (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:320:y:2025:i:c:s0360544225007765

DOI: 10.1016/j.energy.2025.135134

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