# Analysis of Renewable Energy Devices

**DOI:**https://doi.org/10.1007/978-981-10-6963-5_192-1

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## Synonyms

## Definition

Analysis refers to the application of scientific and engineering principles and processes to reveal the properties of a system.

## Introduction

Renewable energy devices may operate in complex internal and external conditions, and engineering analysis is a key element of the design process. Because of the sophisticated physics associated with specific renewable energy devices, simplified analysis is often not adequate for a full understanding of the system behavior. With the advent of information and digital technologies, analysis at various fidelity levels can be achieved using simulation tools. To reduce the computational costs and to validate the accuracy of simulation tools, significant efforts have been invested from both industry and academia.

## Hydrostatic Analysis

*T*has hydrostatic pressure (

*p*) acting on the submerged hull. The pressure is a function of the submerged depth. After a static heel within certain range, the buoy should be able to return to its equilibrium position with the assistance of the restoring moment created by the buoyancy and gravity forces. Details of hydrostatics can be found in Biran and Pulido (2013).

*ϕ*) is relatively large compared to the area under the design overturning moment (straight line), and large safety margin is indicated. Similar analyses can also be found in the works of Lefebvre and Collu (2012) and Karimirad and Michailides (2015).

## Hydrodynamic Analysis

*D*that stands on the seabed, and an incident wave with wavelength of

*λ*and wave height of

*H*is propagating toward the cylinder. Based on Fig. 5 (lower), it is possible to judge which wave forces are of greater significance to the structure. If the cylinder is slender with large

*λ*/

*D*ratio, then viscous forces are prominent due to flow separation. For wind turbines supported by jacket or monopile foundations, the hydrodynamic forces acting on the foundations can often be represented by Morison’s equation (ME); see Morison et al. (1950). Suppose that the slender structure can be divided into many strips, the hydrodynamic force per unit length normal to each strip can be expressed as

*ρ*is the density of seawater,

*D*is the diameter of the slender structure,

*C*

_{M}is the mass coefficient, and

*C*

_{D}is the drag coefficient, \( {\dot{x}}_w \) and \( \ddot{x_w} \) are the velocity and acceleration of water particles at the strip center, and \( {\dot{\eta}}_1 \) and \( \ddot{\eta_1} \) are the velocity and acceleration of the strip. In Eq. (1),

*C*

_{M}and

*C*

_{D}are dependent on the Reynolds number, the Keulegan-Carpenter number, and surface roughness. Reference values are given by offshore standards (NORSOK 2007; DNV 2010). As the strip velocity and acceleration are included in Eq. (1), this equation is also applicable to moving structures. Note that although the ME has been widely applied by industry and academia, this equation ignores lift forces, slamming forces, and axial Froude-Krylov forces.

Hydrodynamic analysis of monopile-type wind turbines using the ME can be found in Veldkamp and Van Der Tempel (2005), Shirzadeh et al. (2013), and Jiang (2018). For monopile foundations supporting 10-megawatt (MW) wind turbines, the diameter can reach 10 m (Velarde 2016), and the ME is not necessarily applicable for short waves. For jacket-type wind turbines, the tubular members have relatively small diameters. For example, the maximum leg diameters of traditional jackets supporting 5-MW wind turbines generally do not exceed 2 m (Chen et al. 2016; Dong et al. 2011). Thus, the hydrodynamic loads are drag-dominated for extreme waves, and the ME is well-suited for the analysis. Shi et al. (2013a, b) performed dynamic loads analysis of jacket-type wind turbines extensively and applied the ME during the hydrodynamic analysis. The ME has also been considered in the hydrodynamic analysis of floating platforms including spar buoy (Jonkman 2007; Jiang et al. 2013b), tension leg platform (Bachynski and Moan 2012), as well as mooring systems (Kvittem et al. 2012).

The panel method is a frequency-domain approach applicable to weakly nonlinear hydrodynamic problems. If there is highly nonlinear interaction between waves and floating bodies, analytical approaches (Faltinsen et al. 2004), the time-domain boundary element approaches (Schløer et al. 2016; Salehyar et al. 2017), or computational fluid dynamics methods (Li and Yu 2012) can be used. Chella et al. (2012) presented an overview of the wave impact forces on OWT substructures. Saletti (2018) studied the bottom slamming phenomenon for a combined wind and wave energy converter.

_{0}is wavelength. Details on wave kinematics can be found in Dean and Dalrymple (1991).

## Aerodynamic and Aeroelastic Analysis

For renewable energy devices that are exposed to wind loads, analysis of wind effect is indispensable. Wind turbines are particularly designed to harness the kinetic energy from the wind, and modern wind turbine blades are long and slender. For horizontal-axis wind turbines (HAWTs), the longest blade announced approaches 90 m for an 8-MW wind turbine (LM Wind Power 2018). Such flexible blades may experience large deformation under the combined effect of wind excitations, centrifugal forces, gravitational forces, and control actions. Aerodynamic analysis helps to understand the behavior of the airflow and the forces acting on the blades and the performance of the wind turbine. The classical blade element moment (BEM) was initially proposed by Glauert (1983) and modified for wind turbine analysis. The basic assumption of the BEM theory is that the force of a blade element is solely responsible for the change of axial momentum of the air which passes through the annulus swept by the elements, and there is no radial interaction between the flows through contiguous annuli (Burton et al. 2011). BEM can be used to calculate the steady loads, the thrust, and the power of HAWTs. A simple BEM algorithm to find the axial and tangential induction factors is presented in Hansen (2008). A BEM algorithm with improved convergence rate is presented in Ning (2014). The classical BEM needs to be corrected by Prandtl’s tip loss factor and Glauert correction to get reasonably good results, as compared to the measurements. Due to unsteadiness of the wind seen by the rotor, the classical BEM cannot realistically capture the aeroelastic behavior of wind turbines, and the unsteady BEM method should be considered. The unsteady BEM, albeit still efficient, considers the time behavior of loads and power by the dynamic wake model and the dynamic change of angle of attack by the dynamic stall model (Hansen 2008). Further, physical phenomena like wake meandering can also be incorporated as engineering corrections to BEM (Larsen et al. 2013).

The BEM theory considers uniform pressure distribution across a rotor plane. Unlike BEM, the generalized dynamic wake (GDW) method, also known as the acceleration potential method, allows for a more general distribution of pressure across a rotor plane and includes inherent modeling of the dynamic wake effect, tip losses, and skewed wake aerodynamics (Moriarty and Hansen 2005). However, the GDW method was developed for lightly loaded rotors at high wind speeds, and the induced velocities are small relative to the mean inflow velocity. Detailed descriptions of the GDW theory can be found in Pitt and Peters (1980) and Suzuki (2000).

Over the past decades, computational fluid dynamics (CFD) has been widely used in aerodynamic analysis of rotors, and actuator disc and actuator line methods are special types of CFD methods (Hansen and Aagaard Madsen 2011). Krogstad and Eriksen (2013) presented a summary of different computational methods that were applied to predict the performance and wake development of a tested model wind turbine. De Vaal et al. (2014) used the actuator disc model to study the effect of surge motion of a floating wind turbine on rotor thrust and induced velocity. Wen et al. (2018) applied the free vortex method to study the power coefficient overshoot of a floating wind turbine in surge oscillations.

Aeroelastic analysis refers to the type of analysis that deals with the interaction between the inertial, elastic, and aerodynamic forces when the structure is exposed to a fluid flow. For commercial wind turbines, stall-induced vibrations and classical flutter are two categories of instabilities that have been observed for stall- and pitch-regulated wind turbines, respectively. Hansen (2003, 2007) presented a state-of-the-art review on aeroelastic stability analysis of wind turbines.

## Integrated Dynamic Analysis

Global motions and structural responses are two main aspects of concern. The global motions refer to the horizontal displacement and rotation of structural members or bodies. For floating wind turbines, rigid body motions of the floating platforms under dynamic loading can provide insights into system dynamics. Nielsen et al. (2006) conducted dynamic response analysis of the floating wind turbine concept HYWIND under wind, wave, and current conditions and compared the simulated and experimental decay tests of tower pitch angle. Pereya et al. (2018) analyzed the nacelle acceleration and platform pitch motion of the TetraSpar floating wind turbine. Such global motion responses, albeit not stated explicitly, can form design constraints for drivetrain components. Kurniawan et al. (2012) performed modeling and global motion analysis of a pitching wave energy converter and discussed dynamics of such a system with different hydraulic components. Muliawan et al. (2013b) conducted dynamic response analysis of a combined wind-wave energy converter and uncovered positive synergy between the two floating bodies by global motion analysis. Shi et al. (2016) developed an ice load force module for an aero-hydro-servo-elastic program and identified important response characteristics of a monopile-type wind turbine under combined ice and wave loads. From an integrated dynamic analysis, structural responses are available. To ensure structural integrity of renewable energy devices, the structural responses need be checked against possible failure modes including fatigue and ultimate limit states. Dong et al. (2011) checked the long-term fatigue damage of tubular joints of a jacket-type OWT (see Fig. 1 right) after performing integrated dynamic analysis. Jiang et al. (2015) analyzed the short-term fatigue damage of mooring lines of a floating wind turbine during shutdown. Wei et al. (2014) calculated the structural capacity of jacket support structure of an OWT under extreme wind and wave loading.

## Analysis of Mechanical Components

Hydraulic components including valves, pumps, accumulators, pipelines, and motors are also mechanical components that have been suggested for use in wave energy converters and wind turbines. Analysis of hydraulic systems often involves mathematical modeling and numerical simulations. Henderson (2006) presented both numerical simulation and laboratory tests of the hydraulic system employed in the Pelamis wave energy converter. Yang et al. (2010) investigated the wear damage in the piston ring and cylinder bore of a heaving-buoy wave energy converter. Numerical simulations of hydraulic transmission of wind turbines can be found in the works of Jiang et al. (2014b), Yang et al. (2015), Buhagiar et al. (2016), and Buhagiar and Sant (2017).

## Code Verification and Validation

A multitude of design codes have been developed and extensively used for analysis of renewable energy devices. In general, many design codes adopt simplified physical representations of actual systems with reduced degrees of freedom but account for most prominent system features. Before being put into use, a new code should be verified against other state-of-the-art codes with adequate model fidelity levels or validated against experimental results. Larsen et al. (2013) showed good comparison between HAWC2 and the CFD code EllipSys3D for aerodynamic forces on a blade. Extensive benchmark work usually involves international collaboration among various academic and industrial partners. Passon et al. (2007) introduced the first international investigation and verification of aeroelastic codes for OWTs. Modeling capabilities of offshore environment, structural modeling, and rotor aerodynamics were compared among nine design codes for four different support structures. Later, code-to-code verifications were conducted of other types of foundations with an increased number of participants and additional load cases; see Jonkman et al. (2008), Popko et al. (2012), and Vorpahl et al. (2014).

Experiments at model scale or full-scale testing are other effective means of code verification. Discrepancies in results between model testing and numerical codes are not uncommon, especially for renewable energy devices that have both aerodynamic and hydrodynamic excitations, because similarity between inertia and viscous forces of the models cannot be achieved simultaneously. Li and Calisal (2010) developed numerical codes using a discrete vortex method for vertical axis tidal current turbines and verified the two- and three-dimensional codes with experiments. Preliminary verification of a wave energy converter design tool with experimental wave tank results is presented in Ruehl et al. (2014). Coulling et al. (2013) verified a numerical model constructed in the design code FAST (Jonkman and Buhl 2005) with 1/50th-scale model test data for a semisubmersible floating wind turbine system. Luan et al. (2018) compared the simulated sectional responses of a semisubmersible using a nonlinear finite element code SIMO-Riflex with the 1/30th-scale model test results.

## Cross-References

## References

- Airy GB (1841) Tides and waves. Encyclopaedia Metropolitana, London, 5, p 241Google Scholar
- American Bureau of Shipping (ABS) (2018) Rules for building and classing mobile offshore drilling units, Part 3, Hull construction and equipment. HoustonGoogle Scholar
- Bachynski EE, Moan T (2012) Design considerations for tension leg platform wind turbines. Mar Struct 29(1):89–114CrossRefGoogle Scholar
- Biran A, Pulido RL (2013) Ship hydrostatics and stability. Butterworth-Heinemann, Oxford, UKGoogle Scholar
- Buhagiar D, Sant T (2017) Modelling of a novel hydro-pneumatic accumulator for large-scale offshore energy storage applications. J Energy Storage 14:283–294CrossRefGoogle Scholar
- Buhagiar D, Sant T, Bugeja M (2016) A comparison of two pressure control concepts for hydraulic offshore wind turbines. J Dyn Syst Meas Control 138(8):081007CrossRefGoogle Scholar
- Burton T, Jenkins N, Sharpe D, Bossanyi E (2011) Wind energy handbook. Wiley, ChichesterCrossRefGoogle Scholar
- Butterfield CP, Musial W, Jonkman J, Sclavounos P, Wayman L (2007) Engineering challenges for floating offshore wind turbines. National Renewable Energy Laboratory, CO, USAGoogle Scholar
- Chella MA, Tørum A, Myrhaug D (2012) An overview of wave impact forces on offshore wind turbine substructures. Energy Procedia 20:217–226CrossRefGoogle Scholar
- Chen I-W, Wong B-L, Lin Y-H, Chau S-W, Huang H-H (2016) Design and analysis of jacket substructures for offshore wind turbines. Energies 9(4):264CrossRefGoogle Scholar
- Coulling AJ, Goupee AJ, Robertson AN, Jonkman JM, Dagher HJ (2013) Validation of a FAST semi-submersible floating wind turbine numerical model with DeepCwind test data. J Renewable Sustainable Energy 5(2):023116CrossRefGoogle Scholar
- Craik AD (2004) The origins of water wave theory. Annu Rev Fluid Mech 36:1–28MathSciNetzbMATHCrossRefGoogle Scholar
- De Vaal J, Hansen ML, Moan T (2014) Effect of wind turbine surge motion on rotor thrust and induced velocity. Wind Energy 17(1):105–121CrossRefGoogle Scholar
- Dean RG, Dalrymple RA (1991) Water wave mechanics for engineers and scientists, vol 2. World Scientific Publishing, SingaporeGoogle Scholar
- DNV (2010) Recommended Practice DNV-RP-C205 Environmental conditions and environmental loads. Høvik, NorwayGoogle Scholar
- DNV GL (2013) Offshore standard DNVGL-OS-C301 Stability and watertight integrity. Høvik, NorwayGoogle Scholar
- Dong W, Moan T, Gao Z (2011) Long-term fatigue analysis of multi-planar tubular joints for jacket-type offshore wind turbine in time domain. Eng Struct 33(6):2002–2014CrossRefGoogle Scholar
- Dong W, Xing Y, Moan T (2012) Time domain modeling and analysis of dynamic gear contact force in a wind turbine gearbox with respect to fatigue assessment. Energies 5(11):4350–4371CrossRefGoogle Scholar
- Faltinsen OM (1993) Sea loads on ships and offshore structures, vol 1. Cambridge University Press, UKGoogle Scholar
- Faltinsen OM, Landrini M, Greco M (2004) Slamming in marine applications. J Eng Math 48(3–4):187–217zbMATHCrossRefGoogle Scholar
- Glauert H (1983) The elements of aerofoil and airscrew theory. Cambridge University Press, UKGoogle Scholar
- Hansen MH (2003) Improved modal dynamics of wind turbines to avoid stall-induced vibrations. Wind Energy 6(2):179–195CrossRefGoogle Scholar
- Hansen MH (2007) Aeroelastic instability problems for wind turbines. Wind Energy 10(6):551–577CrossRefGoogle Scholar
- Hansen MOL (2008) Aerodynamics of wind turbines, 2nd edn. Earthscan, LondonGoogle Scholar
- Hansen MOL, Aagaard Madsen H (2011) Review paper on wind turbine aerodynamics. Trans ASME-I-J Fluids Eng 133(11):114001CrossRefGoogle Scholar
- Harris TA, Kotzalas MN (2007) Rolling bearing analysis: essential concepts of bearing technology, 5th edn. CRC Press/Taylor & Francis Group, Boca RatonGoogle Scholar
- Henderson R (2006) Design, simulation, and testing of a novel hydraulic power take-off system for the Pelamis wave energy converter. Renew Energy 31(2):271–283MathSciNetCrossRefGoogle Scholar
- Jiang Z (2018) The impact of a passive tuned mass damper on offshore single-blade installation. J Wind Eng Ind Aerodyn 176:65–77CrossRefGoogle Scholar
- Jiang Z, Karimirad M, Moan T (2013a) Dynamic response analysis of wind turbines under blade pitch system fault, grid loss, and shutdown events. Wind Energy 17(9):1385–1409Google Scholar
- Jiang Z, Karimirad M, Moan T (2013b) Response analysis of parked spar-type wind turbine considering blade-pitch mechanism fault. Int J Offshore Polar Eng 23(02):120–128Google Scholar
- Jiang Z, Xing Y, Guo Y, Moan T, Gao Z (2014a) Long-term contact fatigue analysis of a planetary bearing in a land-based wind turbine drivetrain. Wind Energy 18(4):591–611CrossRefGoogle Scholar
- Jiang Z, Yang L, Gao Z, Moan T (2014b) Numerical simulation of a wind turbine with a hydraulic transmission system. Energy Procedia 53:44–55CrossRefGoogle Scholar
- Jiang Z, Moan T, Gao Z (2015) A comparative study of shutdown procedures on the dynamic responses of wind turbines. J Offshore Mech Arct Eng 137(1):011904CrossRefGoogle Scholar
- Jiang Z, Zhu X, Hu W (2018) Modeling and analysis of offshore floating wind turbines. In: Advanced wind turbine technology. Springer, New York, USA, pp 247–280CrossRefGoogle Scholar
- Jonkman J (2007) Dynamics modeling and loads analysis of an offshore floating wind turbine, Technical report no. NREL/TP-500-41958, National Renewable Energy Lab.(NREL), GoldenGoogle Scholar
- Jonkman J, Buhl Jr, ML (2005) FAST user’s guide. National Renewable Energy Laboratory, Golden, Technical report no. NREL/EL-500-38230Google Scholar
- Jonkman J, Butterfield S, Passon P, Larsen T, Camp T, Nichols J, Azcona J, Martinez A (2008) Offshore code comparison collaboration within IEA wind annex XXIII: phase II results regarding monopile foundation modeling. Technical report no. NREL/CP-500-47534, National Renewable Energy Lab.(NREL), GoldenGoogle Scholar
- Karimirad M, Michailides C (2015) V-shaped semisubmersible offshore wind turbine: an alternative concept for offshore wind technology. Renew Energy 83:126–143CrossRefGoogle Scholar
- Krogstad P-Å, Eriksen PE (2013) “Blind test” calculations of the performance and wake development for a model wind turbine. Renew Energy 50:325–333CrossRefGoogle Scholar
- Kurniawan A, Pedersen E, Moan T (2012) Bond graph modelling of a wave energy conversion system with hydraulic power take-off. Renew Energy 38(1):234–244CrossRefGoogle Scholar
- Kvittem MI, Bachynski EE, Moan T (2012) Effects of hydrodynamic modelling in fully coupled simulations of a semi-submersible wind turbine. Energy Procedia 24:351–362CrossRefGoogle Scholar
- Larsen TJ (2009) How 2 HAWC2, the user’s manual. Risø National Laboratory, Technical University of Denmark, RoskildeGoogle Scholar
- Larsen TJ, Madsen HA, Larsen GC, Hansen KS (2013) Validation of the dynamic wake meander model for loads and power production in the Egmond aan Zee wind farm. Wind Energy 16(4):605–624CrossRefGoogle Scholar
- Lee C-H (1995) WAMIT theory manual. Massachusetts Institute of Technology, Department of Ocean Engineering. Boston, USAGoogle Scholar
- Lefebvre S, Collu M (2012) Preliminary design of a floating support structure for a 5 MW offshore wind turbine. Ocean Eng 40:15–26CrossRefGoogle Scholar
- Li Y, Calisal SM (2010) Three-dimensional effects and arm effects on modeling a vertical axis tidal current turbine. Renew Energy 35(10):2325–2334CrossRefGoogle Scholar
- Li Y, Yu Y-H (2012) A synthesis of numerical methods for modeling wave energy converter-point absorbers. Renew Sust Energ Rev 16(6):4352–4364CrossRefGoogle Scholar
- LM Wind Power, The worlds’s longest blade. https://www.lmwindpower.com/en/stories-and-press/stories/news-from-lm-places/record-breaking-lm-88-4-blade. Accessed 18 Oct 2018
- Luan C, Gao Z, Moan T (2016) Design and analysis of a braceless steel 5-MW semi-submersible wind turbine. In: ASME 2016 35th international conference on Ocean, Offshore and Arctic Engineering, American Society of Mechanical Engineers, pp V006T009A052-V006T009A052Google Scholar
- Luan C, Gao Z, Moan T (2018) Comparative analysis of numerically simulated and experimentally measured motions and sectional forces and moments in a floating wind turbine hull structure subjected to combined wind and wave loads. Eng Struct 177:210–233CrossRefGoogle Scholar
- McNiff BP, Musial WD, Errichello R (1991) Variations in gear fatigue life for different wind turbine braking strategies. Solar Energy Research Institute, GoldenGoogle Scholar
- Moriarty PJ, Hansen AC (2005) AeroDyn theory manual. Technical report NREL/TP-500-36881, National Renewable Energy Laboratory, GoldenGoogle Scholar
- Morison J, Johnson J, Schaaf S (1950) The force exerted by surface waves on piles. J Pet Technol 2(5):149–154CrossRefGoogle Scholar
- Muliawan MJ, Gao Z, Moan T, Babarit A (2013a) Analysis of a two-body floating wave energy converter with particular focus on the effects of power take-off and mooring systems on energy capture. J Offshore Mech Arct Eng 135(3):031902CrossRefGoogle Scholar
- Muliawan MJ, Karimirad M, Moan T (2013b) Dynamic response and power performance of a combined spar-type floating wind turbine and coaxial floating wave energy converter. Renew Energy 50:47–57CrossRefGoogle Scholar
- Nejad AR, Gao Z, Moan T (2014) On long-term fatigue damage and reliability analysis of gears under wind loads in offshore wind turbine drivetrains. Int J Fatigue 61:116–128CrossRefGoogle Scholar
- Nejad AR, Jiang Z, Gao Z, Moan T (2016) Drivetrain load effects in a 5-MW bottom-fixed wind turbine under blade-pitch fault condition and emergency shutdown. J Phys Conf Ser, vol 11. IOP Publishing, p 112011Google Scholar
- Nielsen FG (2013) Hywind-Deep offshore wind operational experience. 10th Deep Sea Offshore Wind R&D conference, TrondheimGoogle Scholar
- Nielsen FG, Hanson TD, Skaare B (2006) Integrated dynamic analysis of floating offshore wind turbines. In: Proceedings of 25th international conference on offshore mechanics and arctic engineering, pp OMAE2006-92291, HamburgGoogle Scholar
- Ning SA (2014) A simple solution method for the blade element momentum equations with guaranteed convergence. Wind Energy 17(9):1327–1345Google Scholar
- NORSOK (2007) Standard N-003: actions and action effects. Standards Norway, LysakerGoogle Scholar
- Passon P, Kühn M, Butterfield S, Jonkman J, Camp T Larsen TJ (2007) OC3—Benchmark Exercise of Aero-Elastic Offshore Wind Turbine Codes, conference paper NREL/CP-500-41930. The European academy of wind energy special topic conference: the science of making torque from wind, University of Denmark, Lyngby, p 012071Google Scholar
- Pereya BT, Jiang Z, Gao Z, Anderson MT, Stiesdal H (2018) Parametric study of a counter weight suspension system for the tetraspar floating wind turbine. In: Proceedings of the ASME 2018 international offshore wind technical conference, IOWTC 2018, San FranciscoGoogle Scholar
- Pitt DM, Peters DA (1980) Theoretical prediction of dynamic-inflow derivatives. Sixth European rotorcraft and powered lift aircraft forum, BristolGoogle Scholar
- Popko W, Vorpahl F, Zuga A, Kohlmeier M, Jonkman J, Robertson A, Larsen TJ, Yde A, Sætertrø K, Okstad KM (2012) Offshore code comparison collaboration continuation (OC4), phase 1-results of coupled simulations of an offshore wind turbine with jacket support structure. In: Proceedings of the twenty-second international offshore and polar engineering conference. Rhodes, GreeceGoogle Scholar
- Ruehl K, Michelen C, Kanner S, Lawson M, Yu Y-H (2014) Preliminary verification and validation of WEC-Sim, an open-source wave energy converter design tool. In: Proceedings of the ASME 2014 33rd international conference on ocean, offshore and arctic engineering, San Francisco, USA, American Society of Mechanical Engineers, pp V09BT09A040-V009BT009A040Google Scholar
- Salehyar S, Li Y, Zhu Q (2017) Fully-coupled time-domain simulations of the response of a floating wind turbine to non-periodic disturbances. Renew Energy 111:214–226CrossRefGoogle Scholar
- Saletti M (2018) Comparative numerical and experimental study of the global responses of the spar-torus-combination in extreme waves due to the bottom slamming effect. Master thesis, Department of Marine Technology, Norwegian University of Science and Technology, Trondheim, NorwayGoogle Scholar
- Sarpkaya T (2010) Wave forces on offshore structures. Cambridge University Press, New YorkCrossRefGoogle Scholar
- Schløer S, Bredmose H, Bingham HB (2016) The influence of fully nonlinear wave forces on aero-hydro-elastic calculations of monopile wind turbines. Mar Struct 50:162–188CrossRefGoogle Scholar
- Shi W, Park H, Chung C, Baek J, Kim Y, Kim C (2013a) Load analysis and comparison of different jacket foundations. Renew Energy 54:201–210CrossRefGoogle Scholar
- Shi W, Park H, Han J, Na S, Kim C (2013b) A study on the effect of different modeling parameters on the dynamic response of a jacket-type offshore wind turbine in the Korean Southwest Sea. Renew Energy 58:50–59CrossRefGoogle Scholar
- Shi W, Tan X, Gao Z, Moan T (2016) Numerical study of ice-induced loads and responses of a monopile-type offshore wind turbine in parked and operating conditions. Cold Reg Sci Technol 123:121–139CrossRefGoogle Scholar
- Shirzadeh R, Devriendt C, Bidakhvidi MA, Guillaume P (2013) Experimental and computational damping estimation of an offshore wind turbine on a monopile foundation. J Wind Eng Ind Aerodyn 120:96–106CrossRefGoogle Scholar
- Suzuki A (2000) Application of dynamic inflow theory to wind turbine rotors. Doctoral thesis, The University of UtahGoogle Scholar
- Velarde J (2016) Design of monopile foundations to support the DTU 10 MW offshore wind turbine. Master thesis, Department of Marine Technology, Norwegian University of Science and TechnologyGoogle Scholar
- Veldkamp H, Van Der Tempel J (2005) Influence of wave modelling on the prediction of fatigue for offshore wind turbines. Wind Energy 8(1):49–65CrossRefGoogle Scholar
- Vorpahl F, Strobel M, Jonkman JM, Larsen TJ, Passon P, Nichols J (2014) Verification of aero-elastic offshore wind turbine design codes under IEA wind task XXIII. Wind Energy 17(4):519–547CrossRefGoogle Scholar
- Wei K, Arwade SR, Myers AT (2014) Incremental wind-wave analysis of the structural capacity of offshore wind turbine support structures under extreme loading. Eng Struct 79:58–69CrossRefGoogle Scholar
- Wen B, Tian X, Dong X, Peng Z, Zhang W (2018) On the power coefficient overshoot of an offshore floating wind turbine in surge oscillations. Wind Energy 21(11):1076–1091CrossRefGoogle Scholar
- Xing Y, Moan T (2013) Multi-body modelling and analysis of a planet carrier in a wind turbine gearbox. Wind Energy 16(7):1067–1089CrossRefGoogle Scholar
- Yang L, Hals J, Moan T (2010) Analysis of dynamic effects relevant for the wear damage in hydraulic machines for wave energy conversion. Ocean Eng 37(13):1089–1102CrossRefGoogle Scholar
- Yang L, Jiang Z, Gao Z, Moan T (2015) Dynamic analysis of a floating wind turbine with a hydraulic transmission system. In: Proceedings of the twenty-fifth international ocean and polar engineering conference, Hawaii, USAGoogle Scholar