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Comparative parametric analysis of extensible catenary moorings for floating offshore wind turbines

Comparative parametric analysis of extensible catenary moorings for floating offshore wind turbines
Comparative parametric analysis of extensible catenary moorings for floating offshore wind turbines
Extensible mooring lines could play an important part in reducing the cost of mooring systems for floating offshore wind turbines (FOWTs). Mooring designs are driven by extreme loads which determine the required line strength and anchor holding capacity. Incorporating extensible sections to mooring lines reduces the peak loading transmitted to the anchor, enabling smaller, more cost-effective anchors. However, this must be considered alongside increased displacements of the floating platform. Although several extensible tether concepts have been developed to reduce peak loads, their designs have focused on material considerations rather than system response. This paper offers a parametric analysis of extensible moorings for FOWTs, providing insights into relationships between mooring line stiffness, tension reduction, and platform displacements. Fully coupled aero-hydro-servo FEA of the OC4 semi-submersible FOWT were carried-out using the commercial software Flexcom. Length and stiffness of the extensible section were varied and effects on the system were assessed under various load cases. Of the 6 degrees of freedom (DOFs) of a floater, surge has been shown to be most significantly affected by the extensible section. For linear stiffness and below-rated loads, any given reduction in mooring line tension is found to induce a corresponding increase in surge irrespective of extensible section parameters. The trade-off between tension reduction and surge increase is improved when the moorings are subjected to extreme loads, and when the extensible section has a non-linear stiffness.
Festa, Oscar, George
4710abfd-aa37-478e-98c8-21bc2e292384
Gourvenec, Susan
6ff91ad8-1a91-42fe-a3f4-1b5d6f5ce0b8
Sobey, Adam
e850606f-aa79-4c99-8682-2cfffda3cd28
Festa, Oscar, George
4710abfd-aa37-478e-98c8-21bc2e292384
Gourvenec, Susan
6ff91ad8-1a91-42fe-a3f4-1b5d6f5ce0b8
Sobey, Adam
e850606f-aa79-4c99-8682-2cfffda3cd28

Festa, Oscar, George, Gourvenec, Susan and Sobey, Adam (2021) Comparative parametric analysis of extensible catenary moorings for floating offshore wind turbines. In Proceedings of the 5th International Conference on Offshore Renewable Energy (CORE 21).

Record type: Conference or Workshop Item (Paper)

Abstract

Extensible mooring lines could play an important part in reducing the cost of mooring systems for floating offshore wind turbines (FOWTs). Mooring designs are driven by extreme loads which determine the required line strength and anchor holding capacity. Incorporating extensible sections to mooring lines reduces the peak loading transmitted to the anchor, enabling smaller, more cost-effective anchors. However, this must be considered alongside increased displacements of the floating platform. Although several extensible tether concepts have been developed to reduce peak loads, their designs have focused on material considerations rather than system response. This paper offers a parametric analysis of extensible moorings for FOWTs, providing insights into relationships between mooring line stiffness, tension reduction, and platform displacements. Fully coupled aero-hydro-servo FEA of the OC4 semi-submersible FOWT were carried-out using the commercial software Flexcom. Length and stiffness of the extensible section were varied and effects on the system were assessed under various load cases. Of the 6 degrees of freedom (DOFs) of a floater, surge has been shown to be most significantly affected by the extensible section. For linear stiffness and below-rated loads, any given reduction in mooring line tension is found to induce a corresponding increase in surge irrespective of extensible section parameters. The trade-off between tension reduction and surge increase is improved when the moorings are subjected to extreme loads, and when the extensible section has a non-linear stiffness.

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2021-Festa_et_al_CORE - Author's Original
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Published date: 26 August 2021

Identifiers

Local EPrints ID: 457473
URI: http://eprints.soton.ac.uk/id/eprint/457473
PURE UUID: ce24722b-39c7-40fd-a804-808655fb8f5a
ORCID for Susan Gourvenec: ORCID iD orcid.org/0000-0002-2628-7914
ORCID for Adam Sobey: ORCID iD orcid.org/0000-0001-6880-8338

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Date deposited: 09 Jun 2022 16:54
Last modified: 10 Jun 2022 01:48

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