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Wind Energy Science The interactive open-access journal of the European Academy of Wind Energy
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Preprints
https://doi.org/10.5194/wes-2020-29
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/wes-2020-29
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 23 Mar 2020

Submitted as: research article | 23 Mar 2020

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This preprint is currently under review for the journal WES.

Fundamental effect of vibrational mode on vortex-induced vibration in a brimmed diffuser for a wind turbine

Taeyoung Kim1, Hiroto Nagai1, Nobuhide Uda1, and Yuji Ohya2 Taeyoung Kim et al.
  • 1Department of Aeronautics and Astronautics, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan
  • 2Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka, 816-8580, Japan

Abstract. A brimmed diffuser for a wind turbine, also known as a wind lens, is a ring-like short duct that is installed around a rotor. It gathers and accelerates wind to improve the power generation efficiency from the wind turbine, and this effect results from vortex shedding intentionally generated by the brim. However, periodic vortex shedding can induce a vibration in the wind lens structure, which could potentially harm it in the case where resonance occurs when the vortex shedding frequency corresponds to the natural frequency of the wind lens structure. In this study, we investigated the fundamental mechanism of the vortex-induced vibration (VIV) in the brimmed diffuser structure at the Reynolds number of 288. A 2D aeroelastic analysis was conducted, utilizing 2D computational fluid dynamics coupled with the equation of motion in modal space based on the 3D FEM analysis. The 2D aeroelastic analysis provided a reasonable estimation of the critical wind speeds for the actual VIV observed in the wind lens structure. Also, we clarified the vibrational modes critical to the VIV of the wind lens structure, which are the radial and rotational modes of the brimmed diffuser section. Both modes were accompanied by the circumferential bending oscillation of the support arms fixing the brimmed diffuser and were susceptible to the vortex shedding patterns.

Taeyoung Kim et al.

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Taeyoung Kim et al.

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Latest update: 29 May 2020
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Short summary
This study was motivated by a self-induced vibration observed in a wind lens, which is a ring-like diffuser for wind turbines. To reveal the fundamental mechanism of the vortex-induced vibration (VIV) in the brimmed diffuser, a numerical VIV simulation was performed using 3D FEM for modal analysis and 2D CFD for aeroelastic analysis. The result specified the vortex modes and vibration patterns critical to the wind lens structure. Also, this paper suggests how to estimate critical wind speeds.
This study was motivated by a self-induced vibration observed in a wind lens, which is a...
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