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    A post-processing technique for removing ‘irregular frequencies’ and other issues in the results from BEM solvers

    Kelly, Thomas and Zabala, Inaki and Peña-Sanchez, Yerai and Ringwood, John and Henriques, João and Blanco, Jesus M. (2022) A post-processing technique for removing ‘irregular frequencies’ and other issues in the results from BEM solvers. International Journal of Marine Energy, 5 (1). pp. 123-131. ISSN 2214-1669

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    Within the wave energy community, hydrodynamic coefficients obtained from boundary element methods (BEMs) are commonly used to predict the behaviour of wave energy converters (WECs) in response to incident waves. A number of commercially-available BEM solvers exist, with a number of open-source alternatives also available. While open-source solvers have an obvious cost advantage compared to their commercial counterparts, the results from such solvers are often susceptible to so-called ‘irregular frequencies’, which arise from ill-conditioning in boundary integral problems, and result in large under- or over-estimation of hydrodynamic parameters at certain excitation frequencies. Furthermore, while commercial solvers may employ techniques to suppress the effects of irregular frequencies, such solvers may, under certain circumstances, exhibit other problems in the hydrodynamic results produced. For example, the results obtained for the added mass at high frequencies, and the infinite frequency added mass for a water column, may be incorrect. The current work first focusses on an approach to remove the effects of irregular frequencies from the results obtained for the radiation damping of a particular WEC geometry. The use of radiation damping results to obtain values for the added mass, through the use of the Ogilvie relations, is then considered. The technique described herein has been implemented in BEMRosetta, an open-source tool which allows a user to view the results from various BEM solvers, as well as converting input files between solvers. The results presented in this paper have been obtained using the BEMRosetta implementation.

    Item Type: Article
    Keywords: Boundary element methods; Irregular frequencies; Numerical modelling;
    Academic Unit: Faculty of Science and Engineering > Electronic Engineering
    Faculty of Science and Engineering > Research Institutes > Centre for Ocean Energy Research
    Item ID: 16316
    Depositing User: Professor John Ringwood
    Date Deposited: 15 Jul 2022 08:31
    Journal or Publication Title: International Journal of Marine Energy
    Publisher: Elsevier
    Refereed: Yes
    Use Licence: This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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