Nonlinear Evolution of a Steep, Focusing Wave Group in Deep Water Simulated with OceanWave3D

Dylan Barratt*, Harry B. Bingham, Thomas A. A. Adcock

*Corresponding author for this work

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    Abstract

    Steep, focusing waves can experience fast and local nonlinear evolution of the spectrum due to wave-wave interactions resulting in energy transfer to both higher and lower wavenumber components. The shape and kinematics of a steep wave may, thus, differ substantially from the predictions of linear theory. We have investigated the role of nonlinear interactions on group shape for a steep, narrow-banded, directionally-spread wave group focusing in deep water using the fully-nonlinear potential flow solver, OceanWave3D. Exact second-order correction of the initial conditions has been implemented together with a novel third-order approximate correction based on a Stokes-type formulation for surface elevation combined with a scaling argument for the third-order velocity potential. Four-phase separation reveals that the third-order scheme provides a good estimate for the third-order superharmonics. A quantitative assessment of numerical error has also been performed for the spatial and temporal discretization, including energy conservation, a reversibility check and validation against previous simulations performed with a higher-order spectral (HOS) code. The initially narrowbanded amplitude spectrum exhibits the formation of sidelobes at angles of approximately ± 35deg to the spectral peak during the simulated extreme wave event, occurring in approximately 10 wave periods, with a preferential energy transfer to highwavenumber components. The directional energy transfer is attributed to resonant third-order interactions with a discussion of the engineering implications.
    Original languageEnglish
    Article number 021201
    JournalJournal of Offshore Mechanics and Arctic Engineering
    Volume142
    Issue number2
    Number of pages9
    ISSN0892-7219
    DOIs
    Publication statusPublished - 2020

    Keywords

    • Nonlinear wave mechanics
    • Directional energy transfers, wing waves
    • OCEANWAVE3D

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