Performance of a Tethered Point Wave-Energy Absorber in Regular and Irregular Waves
KAUST Grant NumberKAUST-25478-EE08K1
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AbstractThe importance of the mooring system on the dynamic response of a point-absorber type ocean-wave energy converter (WEC) is investigated using a frequency-domain approach. In order to ensure the safety of WECs, careful consideration of the response and resonance frequencies in all motions must be evaluated, including the effects of the mooring system. In this study, a WEC floater with a closed, flat bottom is modeled as a rigid vertical cylinder tethered by elastic mooring lines. The WEC hydrodynamic added mass and damping are obtained using established potential-flow methods, with additional damping provided by the energy-extraction system. The results show that the response of the WEC, and the corresponding power takeoff, varies with the diameter-to-draft (D=T) ratio, mooring system stiffness, and mass distribution. For a given wave climate in Northern California, near San Francisco, the heave energy extraction is found to be best for a shallow WEC with a soft mooring system, compared to other systems that were examined. This result assumes a physical limit (cap) on the motion which is related to the significant wave height to draft ratio. Shallow draft designs, however, may experience excessive pitch motions and relatively larger viscous damping. In order to mitigate the pitch response, the pitch radius of gyration should be small and the center of mass should be low. Copyright © 2010 by ASME.
CitationBachynski EE, Young YL, Yeung RW (2010) Performance of a Tethered Point Wave-Energy Absorber in Regular and Irregular Waves. ASME 2010 7th International Symposium on Fluid-Structure Interactions, Flow-Sound Interactions, and Flow-Induced Vibration and Noise: Volume 3, Parts A and B. Available: http://dx.doi.org/10.1115/fedsm-icnmm2010-30545.
SponsorsThe authors gratefully acknowledge the funding provided byKing Abdullah University of Science and Technology (KAUST)to UC Berkeley, under AEA Award # KAUST-25478-EE08K1.The first author would also like to acknowledge the funding providedby the University of Michigan College of Engineering J.Reid and Polly Anderson Fellowship and a SNAME William M.Kennedy Scholarship.
JournalASME 2010 7th International Symposium on Fluid-Structure Interactions, Flow-Sound Interactions, and Flow-Induced Vibration and Noise: Volume 3, Parts A and B