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    Analytical representation of nonlinear Froude-Krylov forces for 3-DoF point absorbing wave energy devices


    Giorgi, Giuseppe and Ringwood, John (2018) Analytical representation of nonlinear Froude-Krylov forces for 3-DoF point absorbing wave energy devices. Ocean Engineering, 164. pp. 749-759. ISSN 0029-8018

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    Abstract

    Accurate and computationally efficient mathematical models are fundamental for designing, optimizing, and controlling wave energy converters. Many wave energy devices exhibit significant nonlinear behaviour over their full operational envelope, so nonlinear models may become indispensable. Froude-Krylov nonlinearities are of great importance in point absorbers but, in general, their calculation requires an often unacceptable increase in model complexity/computational time. However, for axisymmetric bodies, it is possible to describe the whole geometry analytically, thereby allowing faster calculation of nonlinear Froude-Krylov forces. In this paper, a convenient parametrization of axisymmetric body geometries is proposed, applicable to devices moving in surge, heave, and pitch. While, in general, Froude-Krylov integrals must be solved numerically, by assuming small pitch angles, it is possible to simplify the problem, and achieve a considerably faster algebraic solution. However, both nonlinear models compute in real-time. The framework presented in the paper offers flexibility in terms of computational and fidelity levels, while still representing important nonlinear phenomena such as parametric pitch instability. Models with lower computational requirements may be more suitable for repetitive calculations, such as real-time control, or long-term power production assessment, while higher fidelity models may be more appropriate for maximum load estimation, or short-term power production capability assessment.

    Item Type: Article
    Keywords: Nonlinear Froude-Krylov forces; Wave energy converters; Multi degrees of freedom; Pitching instability; Computational efficiency; Control optimization;
    Academic Unit: Faculty of Science and Engineering > Electronic Engineering
    Faculty of Science and Engineering > Research Institutes > Centre for Ocean Energy Research
    Item ID: 12546
    Identification Number: https://doi.org/10.1016/j.oceaneng.2018.07.020
    Depositing User: Professor John Ringwood
    Date Deposited: 05 Mar 2020 15:51
    Journal or Publication Title: Ocean Engineering
    Publisher: Elsevier
    Refereed: Yes
    URI:

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