Investigation of nonlinear difference-frequency wave excitation on a semisubmersible offshore-wind platform with bichromatic-wave CFD simulations

Lu Wang, Amy Robertson, Jason Jonkman, Yi-Hsiang Yu, Arjen Koop, Adrià Borràs Nadal, Haoran Li, Wei Shi, Romain Pinguet, Yang Zhou, Qing Xiao, Rupesh Kumar, Hamid Sarlak

    Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review

    Abstract

    The natural surge and pitch frequencies of semisubmersible offshore wind platforms are typically designed to be below the wave frequencies to avoid direct excitation. However, surge or pitch resonance can be excited by the nonlinear low-frequency loads generated by irregular incident waves. Second-order potential-flow models with added Morison drag have been found to underpredict this low-frequency excitation and response. As part of the OC6 project1, the authors performed computational fluid dynamics (CFD) simulations to enable a better understanding of the low-frequency loads and the limitations of lower-fidelity models. The focus of this paper is to set up a computationally cost-effective CFD simulation of a fixed semisubmersible platform to investigate nonlinear differencefrequency loads and establish the corresponding uncertainty in the results. Because of the high computing cost, CFD simulations of irregular waves can be challenging. Instead, simulations were performed with bichromatic waves having a shorter repeat period. A preliminary comparison with quadratic transfer functions from second-order potential-flow theory shows that CFD models consistently predict higher nonlinear wave loads at the difference frequency, likely because of flow separation and viscous drag not accounted for in potential-flow theory.
    Original languageEnglish
    Title of host publicationProceedings of the Asme 2021 3rd International Offshore Wind Technical Conference, Iowtc 2021
    Number of pages14
    PublisherThe American Society of Mechanical Engineers (ASME)
    Publication date2021
    Article numberIOWTC2021-3537
    ISBN (Electronic)978-0-7918-8476-8
    DOIs
    Publication statusPublished - 2021
    EventASME 2021 3rd International Offshore Wind Technical Conference - Online event
    Duration: 16 Feb 202117 Feb 2021
    Conference number: 3

    Conference

    ConferenceASME 2021 3rd International Offshore Wind Technical Conference
    Number3
    LocationOnline event
    Period16/02/202117/02/2021

    Fingerprint

    Dive into the research topics of 'Investigation of nonlinear difference-frequency wave excitation on a semisubmersible offshore-wind platform with bichromatic-wave CFD simulations'. Together they form a unique fingerprint.

    Cite this