Uncertainty Assessment of CFD Investigation of the Nonlinear Difference-Frequency Wave Loads on a Semisubmersible FOWT Platform

Research output: Contribution to journalArticlepeer-review

20 Scopus Citations

Abstract

Current mid-fidelity modeling approaches for floating offshore wind turbines (FOWTs) have been found to underpredict the nonlinear, low-frequency wave excitation and the response of semisubmersible FOWTs. To examine the cause of this underprediction, the OC6 project is using computational fluid dynamics (CFD) tools to investigate the wave loads on the OC5-DeepCwind semisubmersible, with a focus on the nonlinear difference-frequency excitation. This paper focuses on assessing the uncertainty of the CFD predictions from simulations of the semisubmersible in a fixed condition under bichromatic wave loading and on establishing confidence in the results for use in improving mid-fidelity models. The uncertainty for the nonlinear wave excitation is found to be acceptable but larger than that for the wave-frequency excitation, with the spatial discretization error being the dominant contributor. Further, unwanted free waves at the difference frequency have been identified in the CFD solution. A wave-splitting and wave load-correction procedure are presented to remove the contamination from the free waves in the results. A preliminary comparison to second-order potential-flow theory shows that the CFD model predicted significantly higher difference-frequency wave excitations, especially in surge, suggesting that the CFD results can be used to better calibrate the mid-fidelity tools.

Original languageAmerican English
Article number64
Pages (from-to)1-25
Number of pages25
JournalSustainability (Switzerland)
Volume13
Issue number1
DOIs
StatePublished - 1 Jan 2021

Bibliographical note

Publisher Copyright:
© 2020 by the authors. Licensee MDPI, Basel, Switzerland.

NREL Publication Number

  • NREL/JA-5000-78248

Keywords

  • Bichromatic waves
  • CFD
  • FOWT
  • IEA Wind
  • Nonlinear wave load
  • OC6
  • Offshore wind
  • QTF
  • Second order
  • Semisubmersible

Fingerprint

Dive into the research topics of 'Uncertainty Assessment of CFD Investigation of the Nonlinear Difference-Frequency Wave Loads on a Semisubmersible FOWT Platform'. Together they form a unique fingerprint.

Cite this