Vortex-induced vibration of spar platforms for floating offshore wind turbines
Vortex-induced vibration of spar platforms for floating offshore wind turbines
An experimental study of flow-induced oscillations of a floating model spar-type wind turbine platform was conducted. The model spar consisted of a floating uniform cylinder moored in a water tunnel test section and free to oscillate about its mooring attachment point near the center of mass. For the bare cylinder, periodic oscillations with figure-eight trajectories were observed over a range of reduced velocities, resembling a lock-in region. This was shown to be a vortex-induced vibration response since the oscillation frequencies and the shedding frequencies stayed equal to each other during the lock-in region. While the lower part of the cylinder was moving upstream at the 2 crossflow extremes of the trajectory, referred to as a counterclockwise (CCW) motion, its upper part experienced clockwise motion. It was hypothesized that the portion of the spar undergoing CCW figure eights is the portion where the flow excites the structure. This hypothesis was then validated by showing that adding helical strakes to the portion of the cylinder with CCW orbital motion suppresses vortex-induced vibration almost entirely, while adding strakes to the portion with clockwise orbital motion had a minimal influence on the amplitude of response.
1169-1176
Carlson, Daniel
c0f88797-732c-46ef-8e74-a5186d4733bf
12 October 2018
Carlson, Daniel
c0f88797-732c-46ef-8e74-a5186d4733bf
Carlson, Daniel and Modarres-Sadeghi, Yahya
(2018)
Vortex-induced vibration of spar platforms for floating offshore wind turbines.
Wind Energy, 21 (11), .
(doi:10.1002/we.2221).
Abstract
An experimental study of flow-induced oscillations of a floating model spar-type wind turbine platform was conducted. The model spar consisted of a floating uniform cylinder moored in a water tunnel test section and free to oscillate about its mooring attachment point near the center of mass. For the bare cylinder, periodic oscillations with figure-eight trajectories were observed over a range of reduced velocities, resembling a lock-in region. This was shown to be a vortex-induced vibration response since the oscillation frequencies and the shedding frequencies stayed equal to each other during the lock-in region. While the lower part of the cylinder was moving upstream at the 2 crossflow extremes of the trajectory, referred to as a counterclockwise (CCW) motion, its upper part experienced clockwise motion. It was hypothesized that the portion of the spar undergoing CCW figure eights is the portion where the flow excites the structure. This hypothesis was then validated by showing that adding helical strakes to the portion of the cylinder with CCW orbital motion suppresses vortex-induced vibration almost entirely, while adding strakes to the portion with clockwise orbital motion had a minimal influence on the amplitude of response.
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Accepted/In Press date: 23 February 2018
e-pub ahead of print date: 25 June 2018
Published date: 12 October 2018
Identifiers
Local EPrints ID: 507206
URI: http://eprints.soton.ac.uk/id/eprint/507206
ISSN: 1095-4244
PURE UUID: cd2d5c8c-8044-4add-a68b-e7bbe20b7534
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Date deposited: 01 Dec 2025 17:43
Last modified: 02 Dec 2025 03:07
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Author:
Daniel Carlson
Author:
Yahya Modarres-Sadeghi
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