Non-Linear Numerical Modeling and Experimental Testing of a Point Absorber Wave Energy Converter

Andrew Stephen Zurkinden, Francesco Ferri, S. Beatty, Jens Peter Kofoed, Morten Kramer

Research output: Contribution to journalJournal articleResearchpeer-review

77 Citations (Scopus)


A time domain model is applied to a three-dimensional point absorber wave energy converter. The dynamical properties of a semi-submerged hemisphere oscillating around a pivot point where the vertical height of this point is above the mean water level are investigated. The numerical model includes the calculation of the non-linear hydrostatic restoring moment by a cubic polynomial function fit to laboratory test results. Moreover, moments due to viscous drag are evaluated on the oscillating hemisphere considering the horizontal and vertical drag force components. The influence on the motions of this non-linear effect is investigated by a simplified formulation proportional to the quadratic velocity. Results from experiments are shown in order to validate the numerical calculations. All the experimental results are in good agreement with the linear potential theory as long as the waves are sufficiently mild i.e. H/λ≤0.02. For steep waves, H/λ≥0.04 however, the relative velocities between the body and the waves increase thus requiring inclusion of the non-linear hydrostatic restoring moment to effectively predict the dynamics of the wave energy converter. For operation of the device with a passively damping power take-off the moment due to viscous drag is found to be negligible
Original languageEnglish
JournalOcean Engineering
Issue numberMarch
Pages (from-to)11-21
Number of pages11
Publication statusPublished - 2014


  • Wave Energy Converter
  • Point Absorber
  • Non-Linear Hydrostatic Moment
  • Non-Linear Drag Moment
  • Linear Potential Theory

Fingerprint Dive into the research topics of 'Non-Linear Numerical Modeling and Experimental Testing of a Point Absorber Wave Energy Converter'. Together they form a unique fingerprint.

  • Cite this