Numerical Analysis of a Floating Offshore Wind Turbine by Coupled Aero-Hydrodynamic Simulation

Abstract

The exploration for renewable and clean energies has become crucial due to environmental issues such as global warming and the energy crisis. In recent years, floating offshore wind turbines (FOWTs) have attracted a considerable amount of attention as a means to exploit steady and strong wind sources available in deep-sea areas. In this study, the coupled aero-hydrodynamic characteristics of a spar-type 5-MW wind turbine are analyzed. An unsteady actuator line model (UALM) coupled with a two-phase computational fluid dynamics solver naoe-FOAM-SJTU is applied to solve three-dimensional Reynolds-averaged Navier–Stokes equations. Simulations with different complexities are performed. First, the wind turbine is parked. Second, the impact of the wind turbine is simplified into equivalent forces and moments. Third, fully coupled dynamic analysis with wind and wave excitation is conducted by utilizing the UALM. From the simulation, aerodynamic forces, including the unsteady aerodynamic power and thrust, can be obtained, and hydrodynamic responses such as the six-degrees-of-freedom motions of the floating platform and the mooring tensions are also available. The coupled responses of the FOWT for cases of different complexities are analyzed based on the simulation results. Findings indicate that the coupling effects between the aerodynamics of the wind turbine and the hydrodynamics of the floating platform are obvious. The aerodynamic loads have a significant effect on the dynamic responses of the floating platform, and the aerodynamic performance of the wind turbine has highly unsteady characteristics due to the motions of the floating platform. A spar-type FOWT consisting of NREL-5-MW baseline wind turbine and OC3-Hywind platform system is investigated. The aerodynamic forces can be obtained by the UALM. The 6DoF motions and mooring tensions are predicted by the naoe-FOAM-SJTU. To research the coupling effects between the aerodynamics of the wind turbine and the hydrodynamics of the floating platform, simulations with different complexities are performed. Fully coupled aero-hydrodynamic characteristics of FOWTs, including aerodynamic loads, wake vortex, motion responses, and mooring tensions, are compared and analyzed.

Keywords

Floating offshore wind turbine / Unsteady aerodynamics / Hydrodynamic responses / Coupling effects / naoe-FOAM-SJTU solver / Actuator line model

References

[1] Archer CL, Jacobson MZ. Evaluation of global wind power. J Geophys Res, 2005, 110(D12): 12110

[2] Bae YH, Kim MH, Shin YS (2010) Rotor-floater-mooring coupled dynamic analysis of mini TLP-type offshore floating wind turbines. the 29 ^th International Conference on Ocean, Offshore and Arctic Engineering, 3:491–498https://doi.org/10.1115/OMAE2010-20555

[3] Bae YH, Kim MH, Yu Q, Kim K (2011) Influence of control strategy to FOWT hull motions by aero-elastic-control-floater-mooring coupled dynamic analysis. Proceedings of the Twenty-first International Offshore and Polar Engineering Conference, Hawaii, USA, June 19–24. International Society of Offshore and Polar Engineers

[4] Butterfield S, Musial W, Jonkman J, Sclavounos P (2005) Engineering challenges for floating offshore wind turbines. Copenhagen Offshore Wind 2005 Conference and Expedition Proceedings, 13(1): 25–28

[5] Digraskar DA (2010) Simulations of flow over wind turbines. Master thesis, University of Massachusetts Amherst

[6] Hansen AM, Laugesen R, Bredmose H, Mikkelsen R, Psichogios N. Small scale experimental study of the dynamic response of a tension leg platform wind turbine. Journal of Renewable and Sustainable Energy, 2014, 6(5): 033104-033465

[7] Henderson AR, Leutz R, Fujii T (2002) Potential for floating offshore wind energy in Japanese waters. Proceedings of the Twelfth International Offshore and Polar Engineering Conference, Kitakyushu, Japan, May 26-31

[8] Henderson AR, Zaaijer MB, Bulder B, Pierik J, Huijsmans R, Van Hees M, Snijders E, Wijnants GH, Wolf MJ (2004) Floating windfarms for shallow offshore sites. Proceedings of the Fourteenth International Offshore and Polar Engineering Conference, Toulon, France, May 23-28

[9] Jagdale S, Ma QW (2010) Practical simulation on motions of a TLP-type support structure for offshore wind turbines. Proceedings of the Twentieth International Offshore and Polar Engineering Conference, Beijing, China, June 20-25

[10] Jonkman J, Musial W (2010) Offshore code comparison collaboration (OC3) for IEA task 23 offshore wind technology and deployment. Office of Scientific & Technical Information Technical Reports. https://doi.org/NREL/TP-5000-48191

[11] Jonkman J, Butterfield S, Musial W, Scott G (2009) Definition of a 5-MW reference wind turbine for offshore system development. Office of Scientific & Technical Information Technical Reports. https://doi.org/10.1002/ajmg.10175

[12] Karimirad M, Moan T (2010) Extreme structural dynamic response of a spar type wind turbine. In AMSE 2010 29th International Conference on Ocean, Offshore and Arctic Engineering: 303–312. https://doi.org/10.1115/OMAE2010-20044

[13] Karimirad M, Moan T. Wave-and wind-induced dynamic response of a spar-type offshore wind turbine. J Waterway Port Coast Ocean Eng, 2012, 138(1): 9-20

[14] Karimirad M, Gao Z, Moan T (2009) Dynamic motion analysis of catenary moored spar wind turbine in extreme environmental condition. Proceedings of the European Offshore Wind Conference, EOW2009, Stockholm, Sweden

[15] Lei H, Zhou D, Lu J, Chen C, Han Z, Bao Y. The impact of pitch motion of a platform on the aerodynamic performance of a floating vertical axis wind turbine. Energy, 2017, 119: 369-383

[16] Li PF, Cheng P, Wan DC (2015) Numerical simulations of wake flows of floating offshore wind turbines by unsteady actuator line model. Proceedings of the 9th International Workshop on Ship and Marine Hydrodynamics, Glasgow, UK, August 26–28

[17] Luo N, Garcés JLP, Seguí YV, Zapateiro M (2012) Dynamic load mitigation for floating offshore wind turbines supported by structures with mooring lines. Proceedings of the 5th European Conference on Structural Control, EACS 2012, Genoa, Italy, June 18-20

[18] Ma Y, Hu Z, Xiao L. Wind-wave induced dynamic response analysis for motions and mooring loads of a spar-type offshore floating wind turbine. J Hydrodyn, 2015, 26(6): 865-874

[19] Matha D, Fischer T, Kuhn M (2009) Model development and loads analysis of an offshore wind turbine on a tension leg platform. the 2009 European Offshore Wind Conference and Exhibition, Stockholm, Sweden, September 14-16

[20] Musial W, Butterfield S, Boone A (2004) Feasibility of floating platform systems for wind turbines. the 23^rd ASME Wind Energy Symposium, Reno, Nevada, January 5-8. https://doi.org/10.2514/6.2004-1007

[21] Nematbakhsh A, Olinger DJ, Tryggvason G. Nonlinear simulation of a spar buoy floating wind turbine under extreme ocean conditions. J Renew Sustain Energ, 2014, 6(3): 708-720

[22] Nielsen FG, Hanson TD, Skaare B. Integrated dynamic analysis of floating offshore wind turbines. Am Soc Mech Eng, 2006, 1: 671-679

[23] Ren N, Li Y, Ou J. Coupled wind-wave time domain analysis of floating offshore wind turbine based on computational fluid dynamics method. J Renew Sustain Energ, 2014, 6(2): 53-86

[24] Roddier D, Cermelli C, Aubault A, Weinstein A. WindFloat: a floating foundation for offshore wind turbines. Journal of Renewable and Sustainable Energy, 2010, 2(3): 53

[25] Sant T, Bonnici D, Farrugia R, Micallef D. Measurements and modelling of the power performance of a model floating wind turbine under controlled conditions. Wind Energy, 2015, 18(5): 811-834

[26] Sebastian T, Lackner MA. Characterization of the unsteady aerodynamics of offshore floating wind turbines. Wind Energy, 2012, 16(3): 339-352

[27] Sørensen JN, Shen WZ. Numerical modeling of wind turbine wakes. J Fluid Eng, 2002, 124: 393-399

[28] Sørensen JN, Shen WZ, Munduate X. Analysis of wake states by a full-field actuator disc model. Wind Energy, 1998, 1(2): 73-88

[29] Stewart G, Lackner M, Robertson A, Jonkamn J, Goupee A (2012) Calibration and validation of a FAST floating wind turbine model of the DeepCwind scaled tension-leg platform. Proceedings for the 22th International Offshore and Polar Engineering Conference, Rhodes, Greece, June 17-22

[30] Tong KC. Technical and economic aspects of a floating offshore wind farm. J Wind Eng Ind Aerodynam s, 1998, 74–76(98): 399-410

[31] Tran TT, Dong HK. The aerodynamic interference effects of a floating offshore wind turbine experiencing platform pitching and yawing motions. Indian J Thoracic Cardiovasc Surg, 2015, 29(2): 549-561

[32] Tran TT, Kim DH. A CFD study into the influence of unsteady aerodynamic interference on wind turbine surge motion. Renew Energy, 2016, 90: 204-228

[33] Wu CK, Nguyen V. Aerodynamic simulations of offshore floating wind turbine in platform-induced pitching motion. Wind Energy, 2017, 20(5): 835-858