0
Research Papers: Structures and Safety Reliability

Influence of Wave Induced Second-Order Forces in Semisubmersible FOWT Mooring Design

[+] Author and Article Information
Carlos Lopez-Pavon

Acciona Energia,
Madrid 28108, Spain
Niobe Tech,
Madrid 28703, Spain
e-mail: carlos@niobetech.com

Rafael A. Watai

Numerical Offshore Tank (TPN),
University of São Paulo,
São Paulo 05508-010, Brazil
e-mail: rafael.watai@tpn.usp.br

Felipe Ruggeri

Numerical Offshore Tank (TPN),
University of São Paulo,
São Paulo 05508-010, Brazil
e-mail: felipe.ruggeri@tpn.usp.br

Alexandre N. Simos

Department of Naval Architecture
and Ocean Engineering,
Escola Politécnica,
University of São Paulo,
São Paulo 05508-010, Brazil
e-mail: alesimos@usp.br

Antonio Souto-Iglesias

Department of Naval Architecture (ETSIN),
Technical University of Madrid (UPM),
Madrid 28040, Spain
e-mail: antonio.souto@upm.es

The so-called low-order methods represent the body geometry by means of flat panels and the velocity potential is considered constant over each panel surface.

One may refer to the discussion provided by Matos et al. [13] on this subject, when dealing with the similar problem of resonant motions of a semi-submersible platform in roll and pitch.

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received July 1, 2013; final manuscript received March 23, 2015; published online April 16, 2015. Editor: Solomon Yim.

J. Offshore Mech. Arct. Eng 137(3), 031602 (Jun 01, 2015) (10 pages) Paper No: OMAE-13-1064; doi: 10.1115/1.4030241 History: Received July 01, 2013; Revised March 23, 2015; Online April 16, 2015

AZIMUT project (Spanish CENIT R&D program) is designed to establish the technological groundwork for the subsequent development of a large-scale offshore wind turbine. The project (2010–2013) has analyzed different alternative configurations for the floating offshore wind turbines (FOWT): SPAR, tension leg platform (TLP), and semisubmersible platforms were studied. Acciona, as part of the consortium, was responsible of scale-testing a semisubmersible platform to support a 1.5 MW wind turbine. The geometry of the floating platform considered in this paper has been provided by the Hiprwind FP7 project and is composed by three buoyant columns connected by bracings. The main focus of this paper is on the hydrodynamic modeling of the floater, with especial emphasis on the estimation of the wave drift components and their effects on the design of the mooring system. Indeed, with natural periods of drift around 60 s, accurate computation of the low-frequency second-order components is not a straightforward task. Methods usually adopted when dealing with the slow-drifts of deep-water moored systems, such as the Newman's approximation, have their errors increased by the relatively low resonant periods of the floating system and, since the effects of depth cannot be ignored, the wave diffraction analysis must be based on full quadratic transfer functions (QTFs) computations. A discussion on the numerical aspects of performing such computations is presented, making use of the second-order module available with the seakeeping software wamit®. Finally, the paper also provides a preliminary verification of the accuracy of the numerical predictions based on the results obtained in a series of model tests with the structure fixed in bichromatic waves.

FIGURES IN THIS ARTICLE
<>
Copyright © 2015 by ASME
Your Session has timed out. Please sign back in to continue.

References

Hanson, T. D., Skaare, B., Yttervik, R., Nielsen, F. G., and Havmoller, O., 2011, “Comparison of Measured and Simulated Responses at the First Full Scale Floating Wind Turbine HYWIND,” Presented at EWEA 2011, European Wind Energy Association, Brussels, Belgium.
Roddier, D., Cermelli, C., Aubault, A., and Weinstein, A., 2010, “Windfloat: A Floating Foundation for Offshore Wind Turbines,” J. Renewable Sustainable Energy, 2(3), p. 033104. [CrossRef]
Nicholls-Lee, R., Micklethwaite, W., Walker, R., and Argall, R., 2014, “Novel, Practical and Effective: A Feasibility Study for a Low Motion, Floating Wind Turbine Platform,” ASME Paper No. OMAE2014-23889.
Marsh, G., 2014, “Greater Role for Composites in Wind Energy,” Reinf. Plast., 58(1), pp. 20–24. [CrossRef]
Viselli, A. M., Goupee, A. J., and Dagher, H. J., 2014, “Model Test of a 1:8 Scale Floating Wind Turbine Offshore in the Gulf of MAINE,” ASME Paper No. OMAE2014-23639. [CrossRef]
Maine International Consulting LLC, 2012, “Floating Offshore Wind Foundations: Industry Consortia and Projects in the United States, Europe and Japan,” Overview Report, Bremen ME.
Goupee, A. J., Koo, B. J., Kimball, R. W., Lambrakos, K. F., and Dagher, H. J., 2014, “Experimental Comparison of Three Floating Wind Turbine Concepts,” ASME J. Offshore Mech. Arctic Eng., 136(2), p. 020906. [CrossRef]
Peiffer, A., Aubault, A., and Weinstein, J., 2011, “A Generic 5 MW Windfloat for Numerical Tool Validation & Comparison Against a Generic Spar,” ASME Paper No. OMAE2011-50278.
Philippe, M., Babarit, A., and Ferrant, P., 2012, “Aero-Hydro-Elastic Simulation of a Semi-Submersible Floating Wind Turbine,” ASME Paper No. OMAE2012-84070. [CrossRef]
Coulling, A. J., Goupee, A. J., Robertson, A. M., and Jonkman, J. M., 2013, “Importance of Second-Order Difference-Frequency Wave-Diffraction Forces in the Validation of a FAST Semi-Submersible Floating Wind Turbine Model,” ASME Paper No. OMAE2013-11072. [CrossRef]
Goupee, A. J., Koo, B., Kimball, R. W., Lambrakos, K. F., and Dagher, H. J., 2012, “Experimental Comparison of Three Floating Wind Turbine Concepts,” ASME Paper No. OMAE2012-83645. [CrossRef]
Newman, J. N., 1974, “Second Order, Slowly Varying Forces on Vessels in Irregular Waves,” International Symposium Dynamics of Marine Vehicles and Structure in Waves, London, Apr. 1–5, pp. 182–186.
Matos, V. L. F., Simos, A. N., and Sphaier, S. H., 2011, “Second-Order Resonant Heave, Roll and Pitch Motions of a Deep-Draft Semi-Submersible: Theoretical and Experimental Results,” Ocean Eng., 38(17–18), pp. 2227–2243. [CrossRef]
Gueydon, S., Duarte, T., Jonkman, J., Bayati, I., and Sarmento, A., 2014, “Comparison of Second Order Loads on a Semisubmersible floating Wind Turbine,” ASME Paper No. OMAE2014-23398. [CrossRef]
Gueydon, S., and Weller, S., 2013, “Study of a Floating Foundation for Wind Turbines,” ASME J. Offshore Mech. Arct. Eng., 135(3), p. 031903. [CrossRef]
Kim, M. H., and Yue, D. K. P., 1989, “The Complete Second-Order Diffraction Solution for an Axisymmetric Body. Part 1. Monochromatic Incident Waves,” J. Fluid. Mech., 200, pp. 235–264. [CrossRef]
Kim, M. H., and Yue, D. K. P., 1990, “The Complete Second-Order Diffraction Solution for an Axisymmetric Body. Part 2. Bichromatic Incident Waves and Body Motions,” J. Fluid. Mech., 211, pp. 557–593. [CrossRef]
Pinkster, J. A., 1980, “Low Frequency Second Order Wave Exciting Forces on Floating Structures,” Ph.D. thesis, Delft University of Technology, The Netherlands.
Lee, C. H., 1995, “Wamit Theory Manual,” Massachusetts Institute of Technology, MIT Report No. 95-2.
WAMIT Inc., 2004, WAMIT User Manual 6.2, 6.2PC, 6.2S, 6.2S-PC, WAMIT Inc., Chestnut Hill, MA.

Figures

Grahic Jump Location
Fig. 2

Catenary mooring system configuration

Grahic Jump Location
Fig. 3

(a) CEHIPAR's model basin main dimensions and (b) view of the semisubmersible model fixed on the carriage

Grahic Jump Location
Fig. 4

Excerpts of records: (a) wave elevation in meters and (b) surge load in kN/m. Test of bichromatic wave with δω = 0.15 rad/s.

Grahic Jump Location
Fig. 5

Higher-order mesh (dipole patches were used to model the heave plates)

Grahic Jump Location
Fig. 6

Free surface meshes used in the second-order analysis (only half mesh is presented as symmetry was considered)

Grahic Jump Location
Fig. 7

First-order excitation force in surge per unit wave amplitude; numerical and experimental results. Values are in real scale.

Grahic Jump Location
Fig. 8

Second-order low-frequency excitation force in surge per wave amplitude squared; numerical and experimental results: (a) tests with δω = 0.15 rad/s; (b) tests with δω = 0.24 rad/s; and (c) tests with δω = 0.34 rad/s. Values are in real scale.

Grahic Jump Location
Fig. 9

Second-order low-frequency excitation force in surge per wave amplitude squared; tests with δω = 0.15 rad/s; numerical results from QTFs (FIX WAM) and Newman's approx. (NEW WAM); Values are in real scale.

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In