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Transformed-FNV: wave forces on a vertical cylinder - a free-surface formulation

Abstract:
Existing force models for a vertical surface-piercing cylinder require water depth integration from the seabed to the free surface to determine the total inline force. However, acquiring the full wave kinematics profiles beneath the water surface presents a significant computational task. We revisit the finite water depth version of the well-known FNV theory (Kristiansen & Faltinsen, 2017, Journal of Fluid Mechanics, 833, 773–805) and propose a transformed version that expresses the total force solely in terms of the fully nonlinear wave properties at the free surface. This novel Transformed-FNV (T-FNV) formulation treats the Morison inertia term exactly and approximates the remaining two convective-derivative type terms with an assumption of slowly varying kinetic energy type terms. We evaluate the accuracy of this transformation against the original formulation, using wave kinematics obtained from fully nonlinear numerical simulations. Two T-FNV formulations are proposed with different input properties required. The first formulation uses the fully nonlinear wave kinematic properties at the free surface, whereas a fully approximated T-FNV formulation requires only the nonlinear freesurface elevation time history measured or calculated at the position of the column but in its absence. Both T-FNV formulations demonstrate good accuracy for wave forces for both deep and shallow-water cases against the original FNV model. The new T-FNV formulations also show the increased role of higher harmonics in the predicted force time histories when compared to those in the free-surface displacement, and the importance of using accurate higher order harmonic wave profiles in nonlinear force calculations.
Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.1016/j.coastaleng.2024.104454

Authors

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Institution:
University of Oxford
Division:
MPLS
Department:
Engineering Science
Role:
Author
ORCID:
0000-0002-6365-9342
More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Engineering Science
Role:
Author
ORCID:
0000-0001-7556-1193


More from this funder
Funder identifier:
https://ror.org/05mmh0f86
Funding agency for:
Tang, T
Grant:
IH200100009
Programme:
TIDE Project
More from this funder
Funder identifier:
https://ror.org/014bj2y47
Funding agency for:
Tang, T
Programme:
Eric and Wendy Schmidt AI in Science Postdoctoral Fellowship
More from this funder
Funder identifier:
https://ror.org/047272k79
Funding agency for:
Tang, T
Programme:
Robert and Maude Gledden Short Stay Visiting Fellowship


Publisher:
Elsevier
Journal:
Coastal Engineering More from this journal
Volume:
189
Article number:
104454
Publication date:
2024-01-19
Acceptance date:
2024-01-05
DOI:
EISSN:
1872-7379
ISSN:
0378-3839


Language:
English
Keywords:
Pubs id:
1595416
Local pid:
pubs:1595416
Deposit date:
2024-01-06
ARK identifier:

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