Parametric excitation of moored wave energy converters using viscous and non-viscous CFD simulations

Johannes Palm, Lars Bergdahl, Claes Eskilsson

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Abstract

The paper discusses the use of CFD simulations to analyse the parametric excitation of moored, full scale wave energy converters in six degrees of freedom. We present results of VOF-RANS and VOF-Euler simulations in OpenFOAM!R for two body shapes: (i) a truncated cylinder; and (ii) a cylinder with a smooth hemispherical bottom. Flow characteristics show large differences in smoothness of flow between the hull shapes, where the smoother shape results in a larger heave response. However the increased amplitude makes it unstable and parametric pitch excitation occurs with amplitudes up to 30". The responses in surge, heave and pitch (including the transition to parametric motion) are found to be insensitive to the viscous effects. This is notable as the converters are working in resonance. The effect of viscous damping was visible in the roll motion, where the RANS simulations showed a smaller roll. However, the roll motion was found to be triggered not by wave-body interaction with the incident wave, but by reflections from the side walls. This highlights the importance of controlling the reflections in numerical wave tanks for simulations with WEC motion in six degrees of freedom.
Original languageEnglish
Title of host publicationAdvances in Renewable Energies Offshore : Proceedings of the 3rd International Conference on Renewable Energies Offshore (RENEW 2018)
EditorsC. Guedes Soares
Place of PublicationLondon
PublisherCRC Press
Publication date2018
Pages455-462
ISBN (Print)978-1-138-58535-5
Publication statusPublished - 2018
Event3rd International Conference on Renewable Energies Offshore - IST, Lisbon, Portugal
Duration: 8 Oct 201810 Oct 2018
Conference number: 3rd

Conference

Conference3rd International Conference on Renewable Energies Offshore
Number3rd
LocationIST
CountryPortugal
CityLisbon
Period08/10/201810/10/2018
SeriesProceedings in marine technology and ocean engineering (Online)
ISSN2638-6461

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Palm, J., Bergdahl, L., & Eskilsson, C. (2018). Parametric excitation of moored wave energy converters using viscous and non-viscous CFD simulations. In C. Guedes Soares (Ed.), Advances in Renewable Energies Offshore: Proceedings of the 3rd International Conference on Renewable Energies Offshore (RENEW 2018) (pp. 455-462). CRC Press. Proceedings in marine technology and ocean engineering (Online)