Comparative Study of Numerical Methods for Predicting Wave-Induced Motions and Loads on a Semisubmersible

Abstract

Numerical simulation tools based on potential-flow theory and/or Morison’s equation are widely used for predicting the hydrodynamic responses of floating offshore wind platforms. In general, these simplified approaches are used for the analysis under operational conditions, albeit with a carefully selected approach to account for viscous effects. Nevertheless, due to the limit hydrodynamic modelling to linear and weakly nonlinear models, these approaches severely underpredict the low-frequency nonlinear wave loads and dynamic responses of a semisubmersible. They may not capture important nonlinearities in severe sea states. For the prediction of wave-induced motions and loads on a semisubmersible, this work systematically compares a fully nonlinear viscous-flow solver and a hybrid model combining the potential-flow theory with Morison-drag loads in steep waves. Results show that when nonlinear phenomena are not dominant, the results obtained by the hybrid model and the high-fidelity method show reasonable agreement, while larger discrepancies occur for highly nonlinear regular waves. Specifically, regular waves with various steepness over different frequencies are focused in the present study, which supplements the understanding in applicability of these two groups of method.

Keywords

Potential flow / Viscous flow / Moored floating body / Steep waves / Motions and loads / CFD

References

[1] ANSYS Aqwa user’s manual release 17.0, 2016, Canonsburg, USA: ANSYS Inc Tech rep

[2] Arent D, Sullivan P, Heimiller D, Lopez A, Eurek K, Badger J, Jorgensen HE, Kelly M, Clarke L, Luckow P. Improved offshore wind resource assessment in global climate stabilization scenarios, 2012, Golden, CO, United States: National Renewable Energy Lab. (NREL)

[3] Barreiro A, Crespo A, Dominguez J, Garcia-Feal O, Zabala I, Gomez-Gesteira M. Quasi-static mooring solver implemented in SPH. Journal of Ocean Engineering and Marine Energy, 2016, 2(3): 381-396

[4] Benitz MA, Schmidt DP, Lackner MA, Stewart GM, Jonkman J, Robertson A. Comparison of hydrodynamic load predictions between reduced order engineering models and computational fluid dynamics for the OC4-DeepCwind semi-submersible. International Conference on Offshore Mechanics and Arctic Engineering, 2014, 45547: V09BT09A006

[5] Benitz MA, Schmidt DP, Lackner MA, Stewart GM, Jonkman J, Robertson A. Validation of hydrodynamic load models using CFD for the OC4-DeepCwind semisubmersible. International Conference on Offshore Mechanics and Arctic Engineering, 2015, 56574: V009T09A037

[6] Burmester S, Vaz G, Gueydon S, el Moctar O. Investigation of a semi-submersible floating wind turbine in surge decay using CFD. Ship Technology Research, 2020, 67(1): 2-14

[7] Coulling AJ, Goupee AJ, Robertson AN, Jonkman JM. Importance of second-order difference-frequency wave-diffraction forces in the validation of a fast semi-submersible floating wind turbine model. International Conference on Offshore Mechanics and Arctic Engineering, 2013, 55423: V008T09A019

[8] Dunbar AJ, Craven BA, Paterson EG. Development and validation of a tightly coupled CFD/6-DOF solver for simulating floating offshore wind turbine platforms. Ocean Engineering, 2015, 110: 98-105

[9] Feng X, Bai W. Hydrodynamic analysis of marine multibody systems by a nonlinear coupled model. Journal of Fluids and Structures, 2017, 70: 72-101

[10] Grilli ST, Guyenne P, Dias F. A fully non-linear model for three-dimensional overturning waves over an arbitrary bottom. International Journal for Numerical Methods in Fluids, 2001, 35(7): 829-867

[11] Guerber E, Benoit M, Grilli ST, Buvat C. A fully nonlinear implicit model for wave interactions with submerged structures in forced or free motion. Engineering Analysis with Boundary Elements, 2012, 36(7): 1151-1163

[12] Gueydon S, Duarte T, Jonkman J. Comparison of second-order loads on a semisubmersible floating wind turbine. International Conference on Offshore Mechanics and Arctic Engineering, 2014, 45530: V09AT09A024

[13] Hague C, Swan C. A multiple flux boundary element method applied to the description of surface water waves. Journal of Computational Physics, 2009, 228(14): 5111-5128

[14] Hirt CW, Nichols BD. Volume of fluid (VOF) method for the dynamics of free boundaries. Journal of Computational Physics, 1981, 39(1): 201-225

[15] Huang Y, Zhuang Y, Wan D. Hydrodynamic study and performance analysis of the OC4-DeepCwind platform by CFD method. International Journal of Computational Methods, 2021, 18(4): 2050020

[16] IEA (2019) Offshore wind outlook 2019: World energy outlook special report. International Energy Agency. https://iea.blob.core.windows.net/assets/98909c1b-aabc-4797-9926-35307b418cdb/WEO019-free.pdf

[17] Jacobsen NG, Fuhrman DR, Fredsøe J. A wave generation toolbox for the open-source CFD library: Openfoam®. International Journal for Numerical Methods in Fluids, 2012, 70(9): 1073-1088

[18] James R, Ros MC (2015) Floating offshore wind: market and technology review. The Carbon Trust, Tech rep

[19] Jiang C. Mathematical modelling of wave-induced motions and loads on moored offshore structures, 2021, Duisburg: University of Duisburg-Essen

[20] Jiang C, el Moctar O. Numerical investigation of wave-induced loads on an offshore monopile using a viscous and a potential-flow solver. Journal of Ocean Engineering and Marine Energy, 2022, 8(3): 381-397

[21] Jiang C, el Moctar O. Extension of a coupled mooring-viscous flow solver to account for mooring-joint-multibody interaction in waves. Journal of Ocean Engineering and Marine Energy, 2023, 9: 93-111

[22] Jiang C, el Moctar O, Schellin TE. Prediction of hydrodynamic damping of moored offshore structures using CFD. International Conference on Offshore Mechanics and Arctic Engineering, 2019, 58776: V002T08A047

[23] Jiang C, el Moctar O, Paredes GM, Schellin TE. Validation of a dynamic mooring model coupled with a RANS solver. Marine Structures, 2020, 72: 102 783

[24] Jiang C, el Moctar O, Schellin TE. Mooring-configurations induced decay motions of a buoy. Journal of Marine Science and Engineering, 2021, 9(3): 350

[25] Jiang C, el Moctar O, Schellin TE. Capability of a potential-flow solver to analyze articulated multibody offshore modules. Ocean Engineering, 2022, 266: 112754

[26] Jonkman J, Musial W. Offshore code comparison collaboration (OC3) for IEA wind task 23 offshore wind technology and deployment, 2010, Golden, CO, United States: National Renewable Energy Lab. (NREL)

[27] Jonkman JM. Dynamics modeling and loads analysis of an offshore floating wind turbine, 2007, Boulder: University of Colorado, 237

[28] Jonkman JM, Buhl ML. FAST user’s guide, Volume 365, 2005, Golden, CO, United States: National Renewable Energy Laboratory

[29] Kvittem MI, Bachynski EE, Moan T. Effects of hydrodynamic modelling in fully coupled simulations of a semi-submersible wind turbine. Energy Procedia, 2012, 24: 351-362

[30] Larsen TJ, Hansen AM (2007) How 2 HAWC2, the user’s manual technical report. Risø National Laboratory. ISSN: 0106–2840 Lee CH (1995) WAMIT theory manual. Massachusetts Institute of Technology, Department of Ocean Engineering

[31] Li H, Bachynski-Polić EE. Analysis of difference-frequency wave loads and quadratic transfer functions on a restrained semi-submersible floating wind turbine. Ocean Engineering, 2021, 232: 109065

[32] Liu Y, Xiao Q, Incecik A, Peyrard C, Wan D. Establishing a fully coupled cfd analysis tool for floating offshore wind turbines. Renewable Energy, 2017, 112: 280-301

[33] Marintek S (2012) Theory manual version 4.6. MARINTEK, Tech rep el

[34] Moctar O, Schellin TE, Söding H (2021) Numerical methods to compute incompressible potential flows. Numerical Methods for Seakeeping Problems, Springer, 17–33

[35] Ormberg H, Passano E. Riflex theory manual, 2012, Trondheim: Marintek

[36] Otter A, Murphy J, Pakrashi V, Robertson A, Desmond C. A review of modelling techniques for floating offshore wind turbines. Wind Energy, 2022, 25(5): 831-857

[37] Pinguet R. Hydrodynamics of semi-submersible floater for offshore wind turbines in highly nonlinear waves using Computational Fluid Dynamics (CFD), and validation of overset meshing technique in a numerical wave tank, 2021, Marseille: Ecole Centrale Marseille

[38] Pinguet R, Kanner S, Benoit M, Molin B (2020) Validation of open-source overset mesh method using free-decay tests of floating offshore wind turbine. The 30th International Ocean and Polar Engineering Conference, ISOPE-I-20-1179

[39] Pinguet R, Kanner S, Benoit M, Molin B. Modeling the dynamics of freely-floating offshore wind turbine subjected to waves with an open-source overset mesh method. International Conference on Offshore Mechanics and Arctic Engineering, 2021, 84768: V001T01A008

[40] Rivera-Arreba I, Bruinsma N, Bachynski EE, Viré A, Paulsen BT, Jacobsen NG. Modeling of a semisubmersible floating offshore wind platform in severe waves. Journal of Offshore Mechanics and Arctic Engineering, 2019, 141(6): 061905

[41] Robertson AN, Jonkman J, Masciola M, Song H, Goupee A, Coulling A, Luan C. Definition of the semisubmersible floating system for phase II of OC4, 2014, Golden, CO, United States: National Renewable Energy Lab. (NREL)

[42] Robertson AN, Jonkman J, Wendt F, Goupee A, Dagher H. Definition of the OC5 DeepCwind semisubmersible floating system, 2016, Golden, CO, United States: National Renewable Energy Lab. (NREL)

[43] Robertson AN, Wendt F, Jonkman JM, Popko W, Dagher H, Gueydon S, Qvist J, Vittori F, Azcona J, Uzunoglu E, Guedes Soares C, Harries R, Yde A, Galinos C, Hermans K, Vaal J, Bozonnet P, Bouy L, Bayati I, Bergua R, Galvan J, Mendikoa I, Sanchez CB, Shin H, Oh S, Molins C, Debruyne Y. OC5 project phase II: validation of global loads of the deepcwind floating semisubmersible wind turbine. Energy Procedia, 2017, 137: 38-57

[44] Robertson AN, Gueydon S, Bachynski E, Wang L, Jonkman J, Alarcón D, Amet E, Beardsell A, Bonnet P, Boudet B, Brun C, Chen Z, Féron M, Forbush D, Galinos C, Galvan J, Gilbert P, Gómez J, Harnois V, Haudin F, Hu Z, Dreff JL, Leimeister M, Lemmer F, Li H, Mckinnon G, Mendikoa I, Moghtadaei A, Netzband S, Oh S, Pegalajar-Jurado A, Nguyen MQ, Ruehl K, Schünemann P, Shi W, Shin H, Si Y, Surmont F, Trubat P, Qwist J, Wohlfahrt-Laymann S. OC6 phase I: Investigating the underprediction of low-frequency hydrodynamic loads and responses of a floating wind turbine. Journal of Physics: Conference Series, 2020, 1618(3): 032033

[45] Rusche H. Computational fluid dynamics of dispersed two-phase flows at high phase fractions, 2003, London: Imperial College London, University of London

[46] Stern F, Diez M, Sadat-Hosseini H, Yoon H, Quadvlieg F. Statistical approach for computational fluid dynamics state-of-the-art assessment: N-version verification and validation. Journal of Verification, Validation and Uncertainty Quantification, 2017, 2(3): 031004

[47] Tran TT, Kim DH. The coupled dynamic response computation for a semi-submersible platform of floating offshore wind turbine. Journal of Wind Engineering and Industrial Aerodynamics, 2015, 147: 104-119

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

[49] Tran TT, Kim DH. A CFD study of coupled aerodynamic-hydrodynamic loads on a semisubmersible floating offshore wind turbine. Wind Energy, 2018, 21(1): 70-85

[50] Wang L, Robertson AN, Jonkman J, Yu YH. Uncertainty assessment of CFD investigation of the nonlinear difference-frequency wave loads on a semisubmersible fowt platform. Sustainability, 2020, 13(1): 64

[51] Wang Y, Chen HC, Vaz G, Burmester S. CFD simulation of semi-submersible floating offshore wind turbine under pitch decay motion. International Conference on Offshore Mechanics and Arctic Engineering, 2019, 59353: V001T01A002

[52] Weller HG, Tabor G, Jasak H, Fureby C. A tensorial approach to computational continuum mechanics using object-oriented techniques. Computers in Physics, 1998, 12(6): 620-631

[53] Wendt FF, Robertson AN, Jonkman JM. Fast model calibration and validation of the oc5-deepcwind floating offshore wind system against wave tank test data. International Journal of Offshore and Polar Engineering, 2019, 29(1): 15-23

[54] Xing T, Stern F. Factors of safety for richardson extrapolation. Journal of Fluids Engineering, 2010, 132(6): 061403

[55] Zhou Y, Xiao Q, Liu Y, Incecik A, Peyrard C, Li S, Pan G. Numerical modelling of dynamic responses of a floating offshore wind turbine subject to focused waves. Energies, 2019, 12(18): 3482