Ocean Renewable Energy Systems (ORES); Wave–Structure Interaction Analysis and Design Methods

A special issue of Journal of Marine Science and Engineering (ISSN 2077-1312). This special issue belongs to the section "Ocean Engineering".

Deadline for manuscript submissions: closed (29 August 2020) | Viewed by 51356

Special Issue Editors


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Guest Editor
Department of Civil Engineering, International Hellenic University (IHU), Thessaloniki, Greece
Interests: wave-structure interaction; offshore wind turbines; wave energy converters; marine civil engineering; offshore and coastal structures; hydrodynamics; marine hydraulics; monitoring technologies in marine engineering
Special Issues, Collections and Topics in MDPI journals
1. State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China
2. Research Institute, Dalian University of Technology in Shenzhen, Shenzhen 518057, China
Interests: offshore wind energy; drivetrain dynamics; wave energy; floating wind turbine; hydrodynamics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Ocean Renewable Energy Systems (ORES) are at a critical crossroad; Offshore Wind Turbines (OWTs) have proven that may lead the energy outlook in years to come and Wave Energy Converters (WECs) are in the critical phase of their reconsideration and redesign. A large number of OWT farms are already in operation while WECs arrays are in the pre-commercial phase. At the same time possible combined ORES or co-located farms and arrays, combining the two technologies are being researched. Successful steps forward, towards safety, sustainability and resilience, are required from both technologies for different reasons but with the same target.

ORES are operating in a very challenging environment where dynamic excitation loads from different sources and with different characteristics need to be considered. The development of numerical analysis models and design methods of ORES as single systems or in OWTs farm and WECs array configurations is a very demanding task. New methods for addressing the wave–structure interaction effects are continuously being developed. Design methods covering the whole life-cycle range of ORES (conception, design, installation, operation, maintenance, dismantling) are continuously redeveloped and reassessed. Novel techniques (e.g. artificial intelligence and smart sensors) are being tested and integrated with various numerical models and design methods.

In this context, this Special Issue invites original scientific contributions on topics including, without being limited to:

Wave–structure interaction and numerical analysis of Ocean Renewable Energy Systems (Offshore Wind Turbines; Wave Energy Converters; combined concepts; multi-purpose ORES).

Numerical modelling and design methods for OWTs farms and WECs arrays.

Co-located OWTs farms and WECs arrays

Near-field (e.g. hydrodynamic, aerodynamic) and far-field (e.g. environmental, coastal erosion) interaction effects of farms and arrays of ORES.

Numerical model and design methods upgrade with the use of physical model experiments, real field data and artificial intelligence.

Risk, reliability, residual strength and resilience of ORES and their structural components.

Numerical methods for Life Cycle Analysis of ORES.

Structural Health Monitoring methods for safety and life extension of ORES.

Dr. Constantine Michailides
Dr. Wei Shi
Guest Editors

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Keywords

  • Fixed bottom and floating Offshore Wind Turbines (OWTs)
  • Wave Energy Converters (WECs)
  • Combined concepts, multi-purpose ORES and co-located OWTs farms and WECs arrays
  • Numerical modelling of OWTs farms and WECs arrays of ORES
  • Design methods of anchors, moorings, foundations and dynamic cabling of ORES
  • Physical model testing of ORES
  • Field measurements and upgrade/integration with numerical analysis tools
  • Numerical methods of installation and operations of ORES
  • Coupling methods and analysis of ORES drivetrains
  • Artificial Intelligence and wave–structure interaction

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Published Papers (13 papers)

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Research

23 pages, 11597 KiB  
Article
Frequency-Based Performance Analysis of an Array of Wave Energy Converters around a Hybrid Wind–Wave Monopile Support Structure
by Sofia Gkaraklova, Pavlos Chotzoglou and Eva Loukogeorgaki
J. Mar. Sci. Eng. 2021, 9(1), 2; https://doi.org/10.3390/jmse9010002 - 22 Dec 2020
Cited by 11 | Viewed by 3097
Abstract
In this paper, we investigate, in the frequency domain, the performance (hydrodynamic behavior and power absorption) of a circular array of four semi-immersed heaving Wave Energy Converters (WECs) around a hybrid wind–wave monopile (circular cylinder). The diffraction/radiation problem is solved by deploying the [...] Read more.
In this paper, we investigate, in the frequency domain, the performance (hydrodynamic behavior and power absorption) of a circular array of four semi-immersed heaving Wave Energy Converters (WECs) around a hybrid wind–wave monopile (circular cylinder). The diffraction/radiation problem is solved by deploying the conventional boundary integral equation method. Oblate-spheroidal and hemispherical-shaped WECs are considered. For each geometry, we assess the effect of the array’s net radial distance from the monopile and of the incident wave direction on the array’s performance under regular waves. The results illustrate that by placing the oblate spheroidal WECs close to the monopile, the array’s power absorption ability is enhanced in the low frequency range, while the opposite occurs for higher wave frequencies. For hemispherical-shaped WECs, the array’s power absorption ability is improved when the devices are situated close to the monopile. The action of oblique waves, with respect to the WECs’ arrangement, increases the absorbed power in the case of oblate spheroidal WECs, while these WECs show the best power absorption ability among the two examined geometries. Finally, for the most efficient array configuration, consisting of oblate spheroidal WECs situated close to the monopile, we utilize an “active” Power Take-Off (PTO) mechanism, facilitating the consideration of a variable with frequency PTO damping coefficient. By deploying this mechanism, the power absorption ability of the array is significantly enhanced under both regular and irregular waves. Full article
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22 pages, 1190 KiB  
Article
Two-Dimensional Numerical Modelling of a Moored Floating Body under Sloping Seabed Conditions
by Aichun Feng, Hooi Siang Kang, Binbin Zhao and Zhiyu Jiang
J. Mar. Sci. Eng. 2020, 8(6), 389; https://doi.org/10.3390/jmse8060389 - 28 May 2020
Cited by 5 | Viewed by 3032
Abstract
A coupled floating body-mooring line model is developed by combining a boundary element model for a two-dimensional floating body and a catenary mooring line model. The boundary element model is formulated in the time domain by a continuous Rankine source, and a reflection [...] Read more.
A coupled floating body-mooring line model is developed by combining a boundary element model for a two-dimensional floating body and a catenary mooring line model. The boundary element model is formulated in the time domain by a continuous Rankine source, and a reflection potential is introduced to account for the wave reflection due to sloping seabed. This newly developed model is validated by comparisons against available data. Then, dynamic response analyses are performed for the moored body in various seabed conditions. Compared with a flat seabed, a sloping seabed causes unsymmetrical mooring line configuration and generates noticeable effects in the motion responses of the floating body. Full article
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14 pages, 4244 KiB  
Article
Local Enhancements of the Mean Drift Wave Force on a Vertical Column Shielded by an Exterior Thin Porous Shell
by Peiwen Cong and Yingyi Liu
J. Mar. Sci. Eng. 2020, 8(5), 349; https://doi.org/10.3390/jmse8050349 - 14 May 2020
Cited by 13 | Viewed by 2449
Abstract
The wave interaction with a vertical column shielded by an exterior porous shell is studied within the framework of potential flow theory. The structures are fixed rigidly at the sea bottom. The interior cylinder is impermeable, and the exterior shell is slightly porous [...] Read more.
The wave interaction with a vertical column shielded by an exterior porous shell is studied within the framework of potential flow theory. The structures are fixed rigidly at the sea bottom. The interior cylinder is impermeable, and the exterior shell is slightly porous and thin. Additionally, the exterior shell is assumed to have fine pores, and a linear pressure drop is adopted at the porous geometry. The mean drift wave force on the system is thereby formulated by two alternative ways, based respectively on the direct pressure integration, i.e., the near-field formulation, and the application of the momentum conservation theorem in the fluid domain, i.e., the far-field formulation. The consistency of the two formulations in calculating the mean drift wave force is assessed for the present problem. Numerical results illustrate that the existence of the porous shell can substantially reduce the mean drift wave force on the interior column. It also appears that the far-field formulation consists of a conventional part as well as an additional part caused by the energy dissipation through the porous geometry. The mean drift wave force on the system is dominated by the first part, which resembles that on an impermeable body. Local enhancements of the mean drift wave force are found at some specific wave frequencies at which certain propagation modes of the fluid satisfy a no-flow condition at the porous shell. Full article
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23 pages, 14455 KiB  
Article
Hydrodynamic Response of a Combined Wind–Wave Marine Energy Structure
by Yapo Wang, Lixian Zhang, Constantine Michailides, Ling Wan and Wei Shi
J. Mar. Sci. Eng. 2020, 8(4), 253; https://doi.org/10.3390/jmse8040253 - 3 Apr 2020
Cited by 40 | Viewed by 4481
Abstract
Due to the energy crisis and greenhouse effect, offshore renewable energy is attracting increasing attention worldwide. Various offshore renewable energy systems, such as floating offshore wind turbines (FOWTs), and wave energy converters (WECs), have been proposed and developed so far. To increase power [...] Read more.
Due to the energy crisis and greenhouse effect, offshore renewable energy is attracting increasing attention worldwide. Various offshore renewable energy systems, such as floating offshore wind turbines (FOWTs), and wave energy converters (WECs), have been proposed and developed so far. To increase power output and reduce related costs, a combined marine energy structure using FOWT and WEC technologies has been designed, analyzed and presented in the present paper. The energy structure combines a 5-MW braceless semisubmersible FOWT and a heave-type WEC which is installed on the central column of the semisubmersible. Wave power is absorbed by a power take-off (PTO) system through the relative heave motion between the central column of the FOWT and the WEC. A numerical model has been developed and is used to determine rational size and draft of the combined structure. The effects of different PTO system parameters on the hydrodynamic performance and wave energy production of the WEC under typical wave conditions are investigated and a preliminary best value for the PTO’s damping coefficient is obtained. Additionally, the effects of viscous modeling used during the analysis and the hydrodynamic coupling on the response of the combined structure are studied. Full article
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20 pages, 14609 KiB  
Article
Investigation of Blade Tip Shape for Improving VAWT Performance
by Yichen Jiang, Chenlu He, Peidong Zhao and Tiezhi Sun
J. Mar. Sci. Eng. 2020, 8(3), 225; https://doi.org/10.3390/jmse8030225 - 22 Mar 2020
Cited by 15 | Viewed by 4922
Abstract
Vertical axis wind turbine (VAWT) is a competitive power generation device due to structural simplicity, wind direction independence, no yaw mechanism required, easier maintenance, and lower noise emission. However, blade tip vortex will be generated at both ends of the blade during the [...] Read more.
Vertical axis wind turbine (VAWT) is a competitive power generation device due to structural simplicity, wind direction independence, no yaw mechanism required, easier maintenance, and lower noise emission. However, blade tip vortex will be generated at both ends of the blade during the rotation, resulting in torque loss and efficiency reduction. In this paper, computational fluid dynamics is used to study blade tip vortex and its reduction technique of a single-blade VAWT rotor in real scale. By monitoring the force and flow field at different heights of the blade, the influence ranges of tip vortex are obtained. The reduction effect of the bulkhead obtained from the blade profile curve is studied, and the size of the bulkhead is optimized. On the basis of adding the optimal bulkhead, the influence of the supporting strut is also explored. The joint action is obtained by changing the location of the supporting strut. The results show that the top supporting strut-bulkhead structure is the optimal position. The power-extraction efficiency of the rotor with this integrated structure is significantly improved at optimal tip speed ratios (TSRs) and higher TSRs. Full article
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19 pages, 5434 KiB  
Article
Analysis of Piled Concrete Foundation for a 3-MW Class Offshore Wind Turbine along the Southwest Coast in Korea
by Hyun-Gi Kim, Bum-Joon Kim and Kwang-Ho Lee
J. Mar. Sci. Eng. 2020, 8(3), 215; https://doi.org/10.3390/jmse8030215 - 20 Mar 2020
Cited by 5 | Viewed by 3643
Abstract
Concrete foundations have received attention as offshore wind turbine support structures because of their various advantages. However, because of the lack of information on structural analysis and the design method of complex marine environmental loads, concrete foundations cannot be applied on actual sites. [...] Read more.
Concrete foundations have received attention as offshore wind turbine support structures because of their various advantages. However, because of the lack of information on structural analysis and the design method of complex marine environmental loads, concrete foundations cannot be applied on actual sites. Therefore, the structure behavior mechanism and concrete reinforcement design need to be evaluated based on soil-structure interactions. Herein, an efficient method for analysis of piled concrete foundations (PCFs) is presented, and the stability of PCF structures is evaluated under environmental conditions of the coast in Korea for a 3-MW wind turbine. Three analytical parameters for PCF models were defined to consider soil-structure interaction. The results of each model were compared with the displacement, stresses, and natural frequencies. Using the analysis results, a prestressing reinforcement design for concrete foundations was proposed. Quasi-static analysis showed that maximum displacement was sufficiently small and the maximum stresses did not exceed the allowable stresses. PCF showed excellent dynamic performance and structural stability. In addition, stiffness of the soil spring model influenced the natural frequency rather than the stiffness of the pile type. Detailed analysis of the connections between piles and concrete need to be studied in the future. Full article
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18 pages, 9529 KiB  
Article
Influence of Central Platform on Hydrodynamic Performance of Semi-Submerged Multi-Buoy Wave Energy Converter
by Yuan Hu, Shaohui Yang, Hongzhou He and Hu Chen
J. Mar. Sci. Eng. 2020, 8(1), 12; https://doi.org/10.3390/jmse8010012 - 23 Dec 2019
Cited by 3 | Viewed by 2474
Abstract
The influence of the central platform on hydrodynamic performance of a wave energy converter (WEC) has remained elusive. To approach this dearth of relevant theoretical research, this paper presents a semi-submerged multi-buoy WEC and the results of the numerical analysis at different dimension [...] Read more.
The influence of the central platform on hydrodynamic performance of a wave energy converter (WEC) has remained elusive. To approach this dearth of relevant theoretical research, this paper presents a semi-submerged multi-buoy WEC and the results of the numerical analysis at different dimension parameters of the central platform of the WEC. The WEC consists of three oscillating buoys hinged with a central platform through multiple actuating arms. Numerical analysis revealed that there exists a relationship between the hydrodynamic performance of device and the geometry of the central platform. At the given wave condition, different central platform size would obviously affect the hydrodynamic performance and wave energy capture width ratio of the semi-submerged multi-buoy WEC. Additionally, appropriately increasing central platform draft would help to improve the wave energy capture capability of the oscillating buoys. Full article
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23 pages, 12129 KiB  
Article
Numerical Study of the Interaction between Level Ice and Wind Turbine Tower for Estimation of Ice Crushing Loads on Structure
by Ming Song, Wei Shi, Zhengru Ren and Li Zhou
J. Mar. Sci. Eng. 2019, 7(12), 439; https://doi.org/10.3390/jmse7120439 - 1 Dec 2019
Cited by 15 | Viewed by 3039
Abstract
In this paper, the interaction between level ice and wind turbine tower is simulated by the explicit nonlinear code LS-DYNA. The isotropic elasto-plastic material model is used for the level ice, in which ice crushing failure is considered. The effects of ice mesh [...] Read more.
In this paper, the interaction between level ice and wind turbine tower is simulated by the explicit nonlinear code LS-DYNA. The isotropic elasto-plastic material model is used for the level ice, in which ice crushing failure is considered. The effects of ice mesh size and ice failure strain on ice forces are investigated. The results indicate that these parameters have a significant effect on the ice crushing loads. To validate and benchmark the numerical simulations, experimental data on level ice-wind turbine tower interactions are used. First, the failure strains of the ice models with different mesh sizes are calibrated using the measured maximum ice force from one test. Next, the calibrated ice models with different mesh sizes are applied for other tests, and the simulated results are compared to corresponding model test data. The effects of the impact speed and the size of wind turbine tower on the comparison between the simulated and measured results are studied. The comparison results show that the numerical simulations can capture the trend of the ice loads with the impact speed and the size of wind turbine tower. When a mesh size of ice model is 1.5 times the ice thickness, the simulations can give more accurate estimations in terms of maximum ice loads for all tests, i.e., good agreement between the simulated and measured results is achieved. Full article
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19 pages, 8544 KiB  
Article
Experimental Analysis on Dynamic Responses of an Electrical Platform for an Offshore Wind Farm under Earthquake Load
by Zhen-Zhou Sun, Chun-Wei Bi, Sheng-Xiao Zhao, Guo-Hai Dong and Hua-Feng Yu
J. Mar. Sci. Eng. 2019, 7(8), 279; https://doi.org/10.3390/jmse7080279 - 18 Aug 2019
Cited by 17 | Viewed by 3669
Abstract
Offshore wind power is gradually developing to more open sea. Considering the economy of power transmission, it will be an inevitable choice to adopt the extra-large electrical platform. The offshore electrical platform is easily affected by sudden extreme loads such as earthquake and [...] Read more.
Offshore wind power is gradually developing to more open sea. Considering the economy of power transmission, it will be an inevitable choice to adopt the extra-large electrical platform. The offshore electrical platform is easily affected by sudden extreme loads such as earthquake and high current loads. With a large volume of electrical equipment arranged on the deck, the offshore electrical platform is characterized as a top-heavy structure in the offshore wind farm. The dynamic effect of the structure will aggravate the vibration problem of the structure. In this paper, a physical model test was carried out to study the dynamic characteristics of the electrical platform of a 10,000-ton offshore converter station under seismic load. The acceleration response, displacement response and stress response of the offshore electrical platform under the typical direction of seismic action were obtained. The effect of the dry–wet environment, mode of seismic excitation, whipping effect and weak positions of electrical platform structure were analyzed. It was determined that the average damping ratio of the first-order mode of the electrical platform was 5.73% and 8.68% with and without water, respectively. The bidirectional seismic excitation was more dangerous to the structure than unidirectional excitation. The peak acceleration along the height of the platform showed a typical whipping effect. Full article
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14 pages, 3404 KiB  
Article
Study on the Optimal Wave Energy Absorption Power of a Float in Waves
by Zhengxiao Luan, Guanghua He, Zhigang Zhang, Penglin Jing, Ruijia Jin, Baolei Geng and Chaogang Liu
J. Mar. Sci. Eng. 2019, 7(8), 269; https://doi.org/10.3390/jmse7080269 - 13 Aug 2019
Cited by 13 | Viewed by 3681
Abstract
The utilization of ocean renewable energy, especially wave energy, is of great significance in ocean engineering. In this study, a three-dimensional numerical wave tank was established to simulate the wave-float interaction based on the Reynolds-averaged Navier–Stokes equations and the Realizable K-Epsilon Two-Layer turbulence [...] Read more.
The utilization of ocean renewable energy, especially wave energy, is of great significance in ocean engineering. In this study, a three-dimensional numerical wave tank was established to simulate the wave-float interaction based on the Reynolds-averaged Navier–Stokes equations and the Realizable K-Epsilon Two-Layer turbulence model was applied. Firstly, convergence studies with respect to the mesh and time step were carried out and confirmed by the published analytical and numerical data. Then, the resonance condition of a particular float was solved by both numerical and analytical methods. The numerical and the analytical results are mutually verified in good agreements, which verify the reliability of the analytical process. Furthermore, a wave energy converter (WEC) consisting of a single float without damping constant was adopted, and its hydrodynamic performance in different wave conditions was investigated. It was found that the damping factor can affect the motion response of the float and the wave force it receives. Under a certain wavelength condition, the WEC resonates with the wave, at which the wave force on the float, displacement of the float and other parameters reach a maximum value. Finally, the influence of linear damping constant on the power take-off (PTO) was studied. The results show that the damping factor does not affect the wave number turning point of the optimal damping constant. Full article
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19 pages, 22459 KiB  
Article
Experimental Investigations on Hydrodynamic Responses of a Semi-Submersible Offshore Fish Farm in Waves
by Yunpeng Zhao, Changtao Guan, Chunwei Bi, Hangfei Liu and Yong Cui
J. Mar. Sci. Eng. 2019, 7(7), 238; https://doi.org/10.3390/jmse7070238 - 23 Jul 2019
Cited by 86 | Viewed by 6773
Abstract
A series of physical model experiments was performed to investigate the hydrodynamic responses of a semi-submersible offshore fish farm in waves. The structural configuration of the fish farm primarily refers to that of the world’s first offshore fish farm, Ocean Farm 1, developed [...] Read more.
A series of physical model experiments was performed to investigate the hydrodynamic responses of a semi-submersible offshore fish farm in waves. The structural configuration of the fish farm primarily refers to that of the world’s first offshore fish farm, Ocean Farm 1, developed by SalMar in Norway. The mooring line tension and motion response of the fish farm were measured at three draughts. The study indicated that the tension on the windward mooring line is greater than that on the leeward mooring line. As the wave height increases, the mooring line tension and motion responses including the heave, surge, and pitch exhibit an upward trend. The windward mooring line tension decreased slightly with increasing draught. The existence of net resulted in approximately 42% reduction in mooring line tension and approximately 51% reduction in surge motion. However, the heave and pitch of the fish farm increased slightly with the existence of net. It was found that the wave parameters, draught, and net have noticeable effect on the hydrodynamic response. Thus, these factors are suggested to be considered in structural designs and optimization to guarantee the ability of the fish farm to resist destruction and ensure safety of workers during intense waves. Full article
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24 pages, 8290 KiB  
Article
Motion Control of Pentapod Offshore Wind Turbines under Earthquakes by Tuned Mass Damper
by Wenhua Wang, Xin Li, Zuxing Pan and Zhixin Zhao
J. Mar. Sci. Eng. 2019, 7(7), 224; https://doi.org/10.3390/jmse7070224 - 16 Jul 2019
Cited by 20 | Viewed by 3385
Abstract
The dynamic characteristics of a bottom-fixed offshore wind turbine (OWT) under earthquakes are analyzed by developing an integrated analysis model of the OWT. Further, the influence of the interactions between the rotor and support system on the structural responses of the OWT subjected [...] Read more.
The dynamic characteristics of a bottom-fixed offshore wind turbine (OWT) under earthquakes are analyzed by developing an integrated analysis model of the OWT. Further, the influence of the interactions between the rotor and support system on the structural responses of the OWT subjected to an earthquake is discussed. Moreover, a passive control method using a tuned mass damper (TMD) is applied to the OWT to control the responses under earthquakes. The effects of the mass ratio, location and tuned frequency of the TMD on controlling structural responses of the OWT under different recorded seismic waves are studied. Full article
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28 pages, 5270 KiB  
Article
Analysis of Dynamic Characteristics of an Ultra-Large Semi-Submersible Floating Wind Turbine
by Zhixin Zhao, Xin Li, Wenhua Wang and Wei Shi
J. Mar. Sci. Eng. 2019, 7(6), 169; https://doi.org/10.3390/jmse7060169 - 1 Jun 2019
Cited by 30 | Viewed by 5798
Abstract
An initial design of the platform for the moderate water depth (100 m) is performed by upscaling of an existing 5 MW braceless semi-submersible platform design to support the DTU (Danish University of Science and Technology) 10 MW wind turbine. To investigate the [...] Read more.
An initial design of the platform for the moderate water depth (100 m) is performed by upscaling of an existing 5 MW braceless semi-submersible platform design to support the DTU (Danish University of Science and Technology) 10 MW wind turbine. To investigate the dynamic characteristics of the ultra-large semi-submersible floating offshore wind turbine (FOWT), an aero-hydro-servo-elastic numerical modeling is applied to carry out the fully coupled time-domain simulation analysis. The motion responses of the ultra-large semi-submersible FOWT are presented and discussed for selected environmental conditions. Based on the quasi-static and dynamic analysis methods, the influence of the dynamic effects of the mooring lines on the platform motion responses and mooring line tension responses are discussed. Subsequently, the difference in the motion responses and structural dynamics of the DTU 10 MW and NREL (National Renewable Energy Laboratory) 5 MW FOWT is studied due to the difference in turbine properties. The simulation results reveal that the excitation of the low-frequency wind loads on the surge and pitch motions, the tower-base fore-aft bending moments and the mooring line tension response becomes more prominent when the size of the wind turbine increases, but the excitation action of the 3P effect on the structural dynamics of the 5 MW FOWT is more obvious than those of the 10 MW FOWT. Full article
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