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Hydrodynamic Analysis and Power Conversion for Point Absorber WEC with Two Degrees of Freedom Using CFD


Point absorber wave energy device with multiple degrees of freedom (DOF) is assumed to have a better absorption ability of mechanical energy from ocean waves. In this paper, a coaxial symmetric articulated point absorber wave energy converter with two degrees of freedom is presented. The mechanical equations of the oscillation buoy with power take-off mechanism (PTO) in regular waves are established. The three-dimensional numerical wave tank is built in consideration of the buoy motion based upon the CFD method. The appropriate simulation elements are selected for the buoy and wave parameters. The feasibility of the CFD method is verified through the contrast between the numerical simulation results of typical wave conditions and test results. In such case, the buoy with single DOF of heave, pitch and their coupling motion considering free (no PTO damping) and damped oscillations in regular waves are simulated by using the verified CFD method respectively. The hydrodynamic and wave energy conversion characteristics with typical wave conditions are analyzed. The numerical results show that the heave and pitch can affect each other in the buoy coupling motion, hydrodynamic loads, wave energy absorption and flow field. The total capture width ratio with two coupled DOF motion is higher than that with a single DOF motion. The wave energy conversion of a certain DOF motion may be higher than that of the single certain DOF motion even though the wave is at the resonance period. When the wave periods are high enough, the interaction between the coupled DOF motions can be neglected.

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  • Abdelkhalik, O., Zou, S.Y., Robinett, R.D., Bacelli, G., Wilson, D.G., Coe, R. and Korde, U., 2017. Multiresonant feedback control of a three-degree-of-freedom wave energy converter, IEEE Transactions on Sustainable Energy, 8(4), 1518–1527.

    Article  Google Scholar 

  • Anbarsooz, M., Passandideh-Fard, M. and Moghiman, M., 2014. Numerical simulation of a submerged cylindrical wave energy converter, Renewable Energy, 64, 132–143.

    Article  Google Scholar 

  • Bachynski, E.E., Young, Y.L. and Yeung, R.W., 2010. Performance of a tethered point wave-energy absorber in regular and irregular waves, Proceedings of the 3rd Joint US-European Fluids Engineering Summer Meeting Collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels, ASME, Montreal, Quebec, Canada.

    Google Scholar 

  • Bernera., 2003. Pelamis wave energy converter, Physical Review B, 68(18), 380–383.

  • Budal, K., Falnes, J., Iversen, L.C., Lillebekken, P.M., Oltedal, G., Hals, T., Onshus, T. and Høy A.S., 1982. The Norwegian wavepower buoy project, Proceedings of the 2nd International Symposium on Wave Energy Utilization, Trondheim, Norway, 323–344.

    Google Scholar 

  • Caska, A.J. and Finnigan, T.D., 2008. Hydrodynamic characteristics of a cylindrical bottom-pivoted wave energy absorber, Ocean Engineering, 35(1), 6–16.

    Article  Google Scholar 

  • Chau, F.P. and Yeung, R.W., 2010. Inertia and damping of heaving compound cylinders, Proceedings of the 25th International Workshop on Water Waves and Floating Bodies, IWWWFB, Harbin, China.

    Google Scholar 

  • Cochet, C. and Yeung, R.W., 2010. Dynamic analysis and configuration design of a two-component wave-energy absorber, Proceedings of the ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering, ASME, Rio de Janeiro, Brazil.

    Google Scholar 

  • Falnes, J. and Budal, K., 1978. Wave-power conversion by point absorbers, Norwegian Maritime Research, 6(4), 2–11.

    Google Scholar 

  • Gao, H. and Yu, Y., 2018. The dynamics and power absorption of cone-cylinder wave energy converters with three degree of freedom in irregular waves, Energy, 143, 833–845.

    Article  Google Scholar 

  • Guo, W., Zhang, L., Zheng X.B. and Wang, S.Q., 2014. Analysis of hydrodynamic performance of wave energy converter based on CFD, Journal of Huazhong University of Science and Technology (Nature Science Edition), 42(7), 22–26. (in Chinese)

    Google Scholar 

  • Henriques, J.C.C., Lopes, M.F.P., Lopes, M.C., Gato, L.M.C. and Dente, A., 2011. Design and testing of a non-linear power take-off simulator for a bottom-hinged plate wave energy converter, Ocean Engineering, 38(11–12), 1331–1337.

    Article  Google Scholar 

  • Jiang, Y.C. and Yeung, R.W., 2012. Computational modeling of rolling cams for wave-energy capture in a viscous fluid, Proceedings of the ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering, ASME, Rio de Janeiro, Brazil.

    Google Scholar 

  • Liu, C.H., Yang, Q.J. and Bao, G., 2018. State-space approximation of convolution term in time domain analysis of a raft-type wave energy converter, Energies, 11(1), 169.

    Article  Google Scholar 

  • Mekhiche, M. and Edwards, K.A., 2014. Ocean power technologies powerbuoy: System-level design, development and validation methodology, Proceedings of the 2nd Marine Energy Technology Symposium, METS, Seattle, USA.

    Google Scholar 

  • Michael, E.M., John, P.C. and Richardson, J.B., 1982. An experimental study of wave power conversion by a heaving, vertical, circular cylinder in restricted waters, Applied Ocean Research, 4(2), 107–112.

    Article  Google Scholar 

  • Peiffer, A., 2009. Modeling and Evaluation of A Wave-energy Device-A Point Absorber with Linear Generator, MSc. Thesis, University of California at Berkeley, Berkeley.

    Google Scholar 

  • Salter, S.H., 1974. Wave power, Nature, 249(5459), 720–724.

    Article  Google Scholar 

  • Ye, Y.Z. and Chen, W.D., 2017. Frequency- and time-domain analysis of a multi-degree-of-freedom point absorber wave energy converter, Advances in Mechanical Engineering, 9(12).

    Google Scholar 

  • Yeung, R.W., Peiffer, A., Tom, N. and Matlak, T., 2010. Design, analysis, and evaluation of the UC-Berkeley wave-energy extractor, Proceedings of the 29th International Conference on Ocean, Offshore, and Arctic Engineering, ASME, Shanghai, China.

    Google Scholar 

  • Zhang, D.H., Li, W., Lin, Y.G. and Bao, J.W., 2012. An overview of hydraulic systems in wave energy application in China, Renewable and Sustainable Energy Reviews, 16(7), 4522–4526.

    Article  Google Scholar 

  • Zhang, L. and Guo, W., 2016. CFD simulation and energy absorption characteristics analysis of a double DOF buoy, Journal of Harbin Institute of Technology, 48(1), 126–132. (in Chinese)

    MathSciNet  Google Scholar 

  • Zhang, L., Guo, W. and Zheng, X.B., 2015. CFD simulation of cylinder buoy heave performance and the flow field analysis, Journal of Huazhong University of Science and Technology (Nature Science Edition), 43(12), 66–70. (in Chinese)

    Google Scholar 

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Correspondence to Wan-chao Zhang.

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Foundation item: This paper is financially supported by the National Natural Science Foundation of China (Grant No. 51579055) and the Natural Science Foundation of Jiangsu Province (Grant No. BK20180980).

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Guo, W., Zhou, Yh., Zhang, Wc. et al. Hydrodynamic Analysis and Power Conversion for Point Absorber WEC with Two Degrees of Freedom Using CFD. China Ocean Eng 32, 718–729 (2018).

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Key words

  • CFD simulation
  • wave energy conversion
  • numerical tank
  • coupling motion
  • capture width ratio