Numerical modelling and wave tank testing of a self-reacting two-body wave energy device

Adi Kurniawan, Matthias Grassow, Francesco Ferri

Research output: Contribution to book/anthology/report/conference proceedingArticle in proceedingResearchpeer-review

Abstract

We study a wave energy device consisting of two concentric floating bodies. The outer body has a long vertical tube inside which the inner body can move relative to the former. Preliminary numerical study uses a frequency-domain model with a linearized drag damping. Surge, heave, and pitch modes are included. Parametric optimization shows that having a tube with enlarged diameter at the bottom improves the power performance relative to device size when compared to a device with uniform tube diameter. Subsequently, small-scale model tests of the device were carried out in a wave tank, both for regular and irregular waves. An eddy current brake simulated the power take off. The measured displacements, absorbed power, and mean drift force in surge from the regular wave tests are generally in good agreement with numerical predictions, except around the pitch resonance period, where the response is significantly larger than predicted. We also observe the occurrence of Mathieu-type instability, where resonant heave motions trigger large pitch/roll oscillations with a period double that of the heave motions. When this happens, relative motion between the two bodies are found to be greatly reduced and hence the absorbed power. A weakly nonlinear time-domain model with heave-dependent pitch restoring moment and pitch-dependent friction force between the two bodies is subsequently developed and is able to predict, to some extent, the occurrence of this behaviour.
Original languageEnglish
Title of host publicationProceedings of the 3rd International Conference on Ships and Offshore Structures : ICSOS 2018
Place of PublicationGothenburg
Publication date2018
Publication statusPublished - 2018
Event3rd International Conference on Ships and Offshore Structures - Chalmers University of Technology, Gothenburg, Sweden
Duration: 17 Sep 201819 Sep 2018
http://www.icsos.info/

Conference

Conference3rd International Conference on Ships and Offshore Structures
LocationChalmers University of Technology
CountrySweden
CityGothenburg
Period17/09/201819/09/2018
Internet address

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Bibliographical note

The conference proceedings is published on a usb.

Keywords

  • Wave Energy Converter
  • Numerical Model
  • Numerical Model Validation
  • Tank Testing
  • Time-Domain Simulations
  • Frequency-Domain Analysis

Cite this

Kurniawan, A., Grassow, M., & Ferri, F. (2018). Numerical modelling and wave tank testing of a self-reacting two-body wave energy device. In Proceedings of the 3rd International Conference on Ships and Offshore Structures: ICSOS 2018