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1
Zhang, Hongjian, Hao Wang, Xin Cai, Jiaojie Xie, Yazhou Wang, and Ningchuan Zhang. "Research on the Dynamic Performance of a Novel Floating Offshore Wind Turbine Considering the Fully-Coupled-Effect of the System." Journal of Marine Science and Engineering 10, no. 3 (March 1, 2022): 341. http://dx.doi.org/10.3390/jmse10030341.
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Floating offshore wind turbines (FOWTs) still face many challenges in improving platform stability. A fully submersible FOWT platform with inclined side columns is designed to tackle the current technical bottleneck of the FOWT platform, combining the structural characteristics of the semi-submersible and Spar platform. An integrated numerical model of FOWT is established considering the fully coupled effect, and the hydrodynamic performance of the novel FOWT, the semi-submersible FOWT, and the Spar FOWT are compared and analyzed under different wave incidence angles and wave frequencies, as well as the blade and tower dynamic response of the three FOWTs under the coupling effect of wind, wave, and current. The results show that the novel floating platform can significantly optimize the hydrodynamic performance and has a better recovery ability after being subjected to external loads. The novel floating platform can significantly reduce the heave peak and its corresponding wave frequency compared to the semi-submersible platform, reducing the possibility of heave resonance. FOWT operation should ensure positive wave inflow as far as possible to avoid excessive wave forces in the lateral direction. Both blade and tower dynamic response are affected by rotor rotation and tower vibration to varying degrees, while tower dynamic response is mainly affected by platform motion. This study suggests that the application of the novel FOWT concept is feasible and can be an alternative in offshore wind exploitation in deep water.
2
Feng, Zhouquan, Yuheng Huang, Xugang Hua, Jinyuan Dai, and Haokun Jing. "Vibration-Resistant Performance Study of a Novel Floating Wind Turbine with Double-Rope Mooring System and Stroke-Limited TMD." Journal of Marine Science and Engineering 11, no. 1 (January 1, 2023): 58. http://dx.doi.org/10.3390/jmse11010058.
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Floating offshore wind turbines (FOWTs) are generally located in the harsh deep-sea environment and are highly susceptible to extreme loads. In order to ensure the normal operation of FOWTs, this article takes the semi-submersible FOWT as an example, proposes a new double-rope mooring system, and studies the dynamic performance of the FOWT with the double-rope mooring system and its effectiveness in reducing the dynamic response of the wind turbine. At the same time, the tuned mass damper (TMD) is installed in the nacelle of the wind turbine, and the TMD parameters are optimized considering the space limitation of the nacelle by limiting the TMD’s stroke, which further reduces the dynamic response of the FOWT and improves its stability. Numerical simulation and analytical studies show that the new double-rope mooring system can reduce the dynamic response of the wind turbine to a greater extent than the traditional single-rope mooring system. Considering the stroke restriction, the control performance of TMD will be slightly weakened, but it is more in line with the actual engineering requirements. Compared with the original FOWT, the proposed new type of FOWT has better dynamic stability and has the prospect of extending to real engineering applications.
3
Xue, Lei, Jundong Wang, Liye Zhao, Zhiwen Wei, Mingqi Yu, and Yu Xue. "Wake Interactions of Two Tandem Semisubmersible Floating Offshore Wind Turbines Based on FAST.Farm." Journal of Marine Science and Engineering 10, no. 12 (December 9, 2022): 1962. http://dx.doi.org/10.3390/jmse10121962.
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Wake effects commonly exist in offshore wind farms, which will cause a 10–20% reduction of whole power production as well as a 5–15% increase of fatigue loading on the wind turbine main structures. Obviously wake interaction between floating offshore wind turbine (FOWT) is more complicated, and needs careful assessment which is a prerequisite for active wake control (AWC). The primary objective of the present research is to investigate in detail how the wake inflow condition, streamwise spacing, turbulence intensity, and wind shear influence the power performance, platform motion dynamic and structural loading of FOWT. FAST.Farm, developed by the National Renewable Energy Laboratory (NREL), was used for simulating two tandem FOWTs in different conditions. Comparisons were made between FOWTs in different conditions on power performance and platform motion dynamic, which were presented through both time and frequency domain analysis. Damage equivalent loads change in FOWTs interference under typical working conditions were discussed and summarized. Half wake inflow would pose many challenges to the downstream FOWT. These research studies can be incorporated into further offshore wind farm wake models, providing applicable AWC strategies to reduce wake interference effects for higher energy production and for the longer life of FOWT.
4
Formosa, W., and T. Sant. "Modelling the loads and motions of a floating offshore wind turbine with asymmetric moorings." Journal of Physics: Conference Series 2362, no. 1 (November 1, 2022): 012013. http://dx.doi.org/10.1088/1742-6596/2362/1/012013.
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Despite the improvements in wind energy conversion technology, wake effects present in wind farms still remain a challenge. In the case of floating offshore wind turbines (FOWTs), these can be mitigated by varying the mooring lengths to dynamically position the FOWTs according to the wind direction. As this introduces asymmetry in the mooring system, the stability of the FOWTs may be affected. With the aim of unlocking the full potential of floating offshore wind, this work investigates the loads and motions of a full-scale 6 MW spar-supported FOWT with four catenary moorings as its position is shifted along the crosswind direction. A hydrodynamic model developed in ANSYS® AQWA™ to obtain the dynamic response of the system in four metocean conditions is presented. Results indicate that asymmetry in the mooring system has a noticeable effect on the sway and roll motions as well as the cable tensions. The wave height and irregularity only appear to influence the FOWT motions. In general, the dynamic response of the FOWT system is not expected to be jeopardized as the typical permissible limits for a spar-supported FOWT and the proof load of the cables were not exceeded.
5
M’zoughi, Fares, Payam Aboutalebi, Izaskun Garrido, Aitor J. Garrido, and Manuel De La Sen. "Complementary Airflow Control of Oscillating Water Columns for Floating Offshore Wind Turbine Stabilization." Mathematics 9, no. 12 (June 12, 2021): 1364. http://dx.doi.org/10.3390/math9121364.
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The implementation and integration of new methods and control techniques to floating offshore wind turbines (FOWTs) have the potential to significantly improve its structural response. This paper discusses the idea of integrating oscillating water columns (OWCs) into the barge platform of the FOWT to transform it into a multi-purpose platform for harnessing both wind and wave energies. Moreover, the OWCs will be operated in order to help stabilize the FOWT platform by means of an airflow control strategy used to reduce the platform pitch and tower top fore-aft displacement. This objective is achieved by a proposed complementary airflow control strategy to control the valves within the OWCs. The comparative study between a standard FOWT and the proposed OWC-based FOWT shows an improvement in the platform’s stability.
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Mostafa, N., M. Murai, R. Nishimura, O. Fujita, and Y. Nihei. "Study of motion of spar-type floating wind turbines in waves with effect of gyro moment at inclination." Journal of Naval Architecture and Marine Engineering 9, no. 1 (June 30, 2012): 67–79. http://dx.doi.org/10.3329/jname.v9i1.10732.
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Recently, a number of research groups have paid much attention to the study of Floating Offshore Wind Turbines (FOWTs). Similar to other offshore structures, the FOWTs are subjected to irregular waves and wind loads which cause a dynamic response in the structures. Under marine environmental conditions, they face many forces which prevent them from floating in the upright condition; they incline as a result of the winds, strong currents, typhoons, cyclones, storms etc. The motion of the FOWT might be changed by a change in gyroscopic effect which depends on the angular velocity and moment of inertia of the blade. Therefore, to investigate the effect of the gyro moment on the motion of the FOWT, two types of experiment were carried out in a water tank using a 1/360 scale model of a prototype FOWT. Firstly, the interaction between the rotary motion of the wind turbine blade and the dynamic motion of the SPAR-type FOWT was studied at small angles of inclination in regular waves. Secondly, the interaction between the change of rotational speed as well as moment of inertia of the blade and the motion of the FOWT was studied. In this paper, numerical calculations have been carried out using potential theory based on the 3D panel method. Finally, the experimental results are compared with the results of numerical simulation and findings are discussed. DOI: http://dx.doi.org/10.3329/jname.v9i1.10732 Journal of Naval Architecture and Marine Engineering 9(2012) 67-79
7
Dong, Yehong, Yewen Chen, Hao Liu, Shuni Zhou, Yuanxiang Ni, Chang Cai, Teng Zhou, and Qing’an Li. "Review of Study on the Coupled Dynamic Performance of Floating Offshore Wind Turbines." Energies 15, no. 11 (May 27, 2022): 3970. http://dx.doi.org/10.3390/en15113970.
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Floating offshore wind turbines (FOWT) have attracted more and more attention in recent years. However, environmental loads on FOWTs have higher complexity than those on the traditional onshore or fixed-bottom offshore wind turbines. In addition to aerodynamic loads on turbine blades, hydrodynamic loads also act on the support platform. A review on the aerodynamic analysis of blades, hydrodynamic simulation of the supporting platform, and coupled aero- and hydro-dynamic study on FOWTs, is presented in this paper. At present, the primary coupling method is based on the combination of BEM theory and potential flow theory, which can simulate the performance of the FOWT system under normal operating conditions but has certain limitations in solving the complex problem of coupled FOWTs. The more accurate and reliable CFD method used in the research of coupling problems is still in its infancy. In the future, multidisciplinary theories should be used sufficiently to research the coupled dynamics of hydrodynamics and aerodynamics from a global perspective, which is significant for the design and large-scale utilization of FOWT.
8
Lee, Y.-J., C. Y. Ho, and Z. Z. Huang. "Hydrodynamic Responses of a Spar-Type Floating Wind Turbine in High Waves." Journal of Mechanics 31, no. 1 (October 21, 2014): 105–12. http://dx.doi.org/10.1017/jmech.2014.69.
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AbstractFloating offshore wind turbines (FOWTs) can be used to exploit the enormous wind energy present over deep waters. Numerous studies have examined the dynamics of FOWTs, but few have focused on validating numerical results with experimental results, particularly for a deep draught FOWT in regions with frequent tropical storms. For this study, we developed a computer code and conducted experiments with a scale model to validate the simulation results. The computer code was first verified by comparing the results with those of the International Energy Agency Wind Task 23. Numerical simulations were implemented in both the frequency domain and the time domain. A comparison of the numerical and experimental results of the scale model in high waves showed good agreement. The flexibility of blades and the tower did not observably affect the motion of the deep draft spar-type FOWT. Therefore, it can be ignored in the preliminary design. The pitch motion of the scale model was within 1°. Therefore, the spar-type FOWT may be an effective power source for regions with frequent tropical storms.
9
Jia, Zhaolin, Han Wu, Hao Chen, Wei Li, Xinyi Li, Jijian Lian, Shuaiqi He, Xiaoxu Zhang, and Qixiang Zhao. "Hydrodynamic Response and Tension Leg Failure Performance Analysis of Floating Offshore Wind Turbine with Inclined Tension Legs." Energies 15, no. 22 (November 16, 2022): 8584. http://dx.doi.org/10.3390/en15228584.
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The tension legs are the essential parts of the tension legs platform-type (TLP-type) floating offshore wind turbine (FOWT) against the extra buoyancy of FOWT. Therefore, the TLP-type FOWT will face the risk of tension leg failure. However, there are seldom analyses on the hydrodynamic response and tension leg failure performance of FOWT with inclined tension legs. In this paper, a hydrodynamic model was established using three-dimensional hydrodynamic theory and applied in the motion response and tension analyses of FOWT with conventional and new tension leg arrangements on Moses. The influence of draft and tension leg arrangement on the performance of FOWT with inclined tension legs were studied. The optimum draft was the height of the column and lower tensions were obtained for the new tension leg arrangement. Moreover, the tension leg failure performance of FOWT with inclined tension legs was evaluated under different failure conditions. The results illustrated that the FOWT with the new tension leg arrangement can still operate safely after one tension leg fails.
10
Dinh, Van Nguyen, and Biswajit Basu. "On the Modeling of Spar-Type Floating Offshore Wind Turbines." Key Engineering Materials 569-570 (July 2013): 636–43. http://dx.doi.org/10.4028/www.scientific.net/kem.569-570.636.
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In this paper an overview about floating offshore wind turbines (FOWT) including operating conditions, property and applicability of the barge, tension-leg, and spar floating platforms is described. The spar-floating offshore wind turbines (S-FOWT) have advantages in deepwater and their preliminary design, numerical modeling tools and integrated modeling are reviewed. Important conclusions about the nacelle and blade motions, tower response, effects of wind and wave loads, overall vibration and power production of the S-FOWT are summarized. Computationally-simplified models with acceptable accuracy are necessary for feasibility and pre-engineering studies of the FOWT. The design needs modeling and analysis of aero-hydro-servo dynamic coupling of the entire FOWT. This paper also familiarizes authors with FOWT and its configurations and modeling approaches.
11
Walker, Jake, Andrea Coraddu, Maurizio Collu, and Luca Oneto. "Digital twins of the mooring line tension for floating offshore wind turbines to improve monitoring, lifespan, and safety." Journal of Ocean Engineering and Marine Energy 8, no. 1 (September 24, 2021): 1–16. http://dx.doi.org/10.1007/s40722-021-00213-y.
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AbstractThe number of installed floating offshore wind turbines (FOWTs) has doubled since 2017, quadrupling the total installed capacity, and is expected to increase significantly over the next decade. Consequently, there is a growing consideration towards the main challenges for FOWT projects: monitoring the system’s integrity, extending the lifespan of the components, and maintaining FOWTs safely at scale. Effectively and efficiently addressing these challenges would unlock the wide-scale deployment of FOWTs. In this work, we focus on one of the most critical components of the FOWTs, the Mooring Lines (MoLs), which are responsible for fixing the structure to the seabed. The primary mechanical failure mechanisms in MoLs are extreme load and fatigue, both of which are functions of the axial tension. An effective solution to detect long-term drifts in the mechanical response of the MoLs is to develop a Digital Twin (DT) able to accurately predict the behaviour of the healthy system to compare with the actual one. Moreover, we will develop another DT able to accurately predict the near future axial tension as an effective tool to improve the lifespan of the MoLs and the safety of FOWT maintenance operations. In fact, by changing the FOWT operational settings, according to the DT prediction, operators can increase the lifespan of the MoLs by reducing the stress and, additionally, in the case where FOWT operational maintenance is in progress, the prediction from the DT can serve as early safety warning to operators. Authors will leverage operational data collected from the world’s first commercial floating-wind farm [the Hywind Pilot Park (https://www.equinor.com/en/what-we-do/floating-wind/hywind-scotland.html.)] in 2018, to investigate the effectiveness of DTs for the prediction of the MoL axial tension for the two scenarios depicted above. The DTs will be developed using state-of-the-art data-driven methods, and results based on real operational data will support our proposal.
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Zalkind, Daniel, Nikhar J. Abbas, John Jasa, Alan Wright, and Paul Fleming. "Floating wind turbine control optimization." Journal of Physics: Conference Series 2265, no. 4 (May 1, 2022): 042021. http://dx.doi.org/10.1088/1742-6596/2265/4/042021.
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Abstract We present a framework for optimizing the control parameters of floating offshore wind turbines (FOWTs). The framework combines aeroelastic simulations with a systems engineering model and control software. In an example of the optimization framework, we minimize tower damage equivalent loading with generator speed constraints. We also study the effect of thrust-limiting control and quantify the trade off between fatigue loading and energy capture using a set of optimal controller designs. Finally, we optimize the controller of four different FOWT models and compare their dynamic responses. Additional details and other use cases for the framework are presented, which can optimize different control problems and evaluate FOWT designs.
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Zhai, Yuting, Haisheng Zhao, Xin Li, and Wei Shi. "Hydrodynamic Responses of a Barge-Type Floating Offshore Wind Turbine Integrated with an Aquaculture Cage." Journal of Marine Science and Engineering 10, no. 7 (June 22, 2022): 854. http://dx.doi.org/10.3390/jmse10070854.
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The dynamic responses of a new structure combining a barge-type floating offshore wind turbine and an aquaculture cage is investigated numerically. First, a 5 MW barge-type floating offshore wind turbine with an aquaculture cage (FOWT-AC) is designed and the numerical model is established in ANSYS-AQWA. The numerical model of the barge-type FOWT-AC is then checked, and the natural periods of the six degrees of freedom motion satisfy the recommendations of the DNV specification. Based on the reasonable model, the comparison study of dynamic responses between the barge-type FOWT-AC and FOWT under the environmental conditions of the South China Sea is carried out, and it is observed that the FOWT-AC produces a basically lower standard deviation of the motion responses. To investigate the new structure of the barge-type FOWT-AC deeply, the analyses of second-order hydrodynamic response, typical environmental conditions and the mooring line breaking scenario are carried out. The simulation results show that the second-order wave loads increase the dynamic response of the barge-type FOWT-AC slightly unless it causes resonance for the structure. In addition, the motion responses of the floating structures increase significantly when the currents are applied, especially when the aquaculture cage is integrated into the barge-type FOWT. When one of the mooring lines connected to the offshore or onshore side of the platform breaks, the presence of the aquaculture cage results in a smaller standard deviation in the motion responses of the coupled structure, which means that the barge-type FOWT-AC structure is more stable.
14
Basbas, Hedi, Yong-Chao Liu, Salah Laghrouche, Mickaël Hilairet, and Franck Plestan. "Review on Floating Offshore Wind Turbine Models for Nonlinear Control Design." Energies 15, no. 15 (July 28, 2022): 5477. http://dx.doi.org/10.3390/en15155477.
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This article proposes a review of the modeling approaches for floating offshore wind turbines (FOWTs) for nonlinear control design. The aerodynamic, hydrodynamic and mooring line dynamic modules for the FOWT have been reviewed to provide an overview of several modeling approaches with their respective features. Next, three control-oriented models from the literature are revisited by presenting their methodological approaches to modeling and identification. These three models cover the three most popular types of FOWTs. Then, the performances of these models are validated with the open fatigue, aerodynamics, structures, and turbulence (OpenFAST) code, and their performances are evaluated according to several criteria. Finally, one of the three models is used to illustrate a nonlinear second-order sliding mode control based on the twisting algorithm to optimize the performance of the FOWT in terms of energy extraction and reduction in the platform pitch oscillation.
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Wang, Yapo, Lixian Zhang, Constantine Michailides, Ling Wan, and Wei Shi. "Hydrodynamic Response of a Combined Wind–Wave Marine Energy Structure." Journal of Marine Science and Engineering 8, no. 4 (April 3, 2020): 253. http://dx.doi.org/10.3390/jmse8040253.
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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.
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Zhou, Yiming, Sensen Feng, Xiaojiang Guo, Feng Tian, Xu Han, Wei Shi, and Xin Li. "Initial Design of a Novel Barge-Type Floating Offshore Wind Turbine in Shallow Water." Journal of Marine Science and Engineering 11, no. 3 (February 21, 2023): 464. http://dx.doi.org/10.3390/jmse11030464.
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The studies on floating offshore wind turbines (FOWTs) have been increasing over recent decades due to the growing interest in offshore renewable energy. The present paper proposes a barge platform with four moonpools to support the Technical University of Denmark 10 MW wind turbine for a designed water depth of 60 m. A 4 × 2 mooring system with eight mooring lines is also proposed for the barge platform. The main dimensions of the barge platform are optimally selected with respect to its preliminary hydrodynamic properties and potential financial benefit. The proposed barge-type FOWT is then demonstrated to be aligned with the DNV standard requirements in terms of its intact and damage stability. Furthermore, coupled time-domain simulations are conducted for the proposed barge FOWT with mooring under the selected environmental and operational conditions by using Simo-Riflex-AeroDyn (SRA). Through decay test simulations, the natural periods of the barge-type FOWT are demonstrated to be within the DNV recommended ranges. The proposed mooring system is also benchmarked with the 3 × 3 mooring concept that was used for a 3 MW barge-type FOWT installed in Kitakyushu. The response magnitudes of the barge platform and mooring line tension are similar to both mooring systems, and thus the 4 × 2 mooring system is preferred due to its lower cost. In addition, the proposed barge platform is preliminarily demonstrated to be able to survive for the 50-year extreme environmental conditions under parked wind turbine status, as well as the normal environmental conditions under the operating status.
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Amaral, Giovanni, Pedro Mello, Lucas do Carmo, Izabela Alberto, Edgard Malta, Alexandre Simos, Guilherme Franzini, Hideyuki Suzuki, and Rodolfo Gonçalves. "Seakeeping Tests of a FOWT in Wind and Waves: An Analysis of Dynamic Coupling Effects and Their Impact on the Predictions of Pitch Motion Response." Journal of Marine Science and Engineering 9, no. 2 (February 10, 2021): 179. http://dx.doi.org/10.3390/jmse9020179.
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The present work highlights some of the dynamic couplings observed in a series of tests performed in a wave basin with a scaled-model of a Floating Offshore Wind Turbine (FOWT) with semi-submersible substructure. The model was moored by means of a conventional chain catenary system and an actively controlled fan was used for emulating the thrust loads during the tests. A set of wave tests was performed for concomitant effects of not aligned wave and wind. The experimental measurements illustrate the main coupling effects involved and how they affect the FOWT motions in waves, especially when the floater presents a non-negligible tilt angle. In addition, a frequency domain numerical analysis was performed in order to evaluate its ability to capture these effects properly. The influence of different modes of fan response, floater trim angles (changeable with ballast compensation) and variations in the mooring stiffness with the offsets were investigated in the analysis. Results attest that significant changes in the FOWT responses may indeed arise from coupling effects, thus indicating that caution must be taken when simplifying the hydrodynamic frequency-domain models often used as a basis for the simulation of FOWTs in waves and in optimization procedures for the design of the floater and mooring lines.
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Villoslada, Daniel, Matilde Santos, and María Tomás-Rodríguez. "General Methodology for the Identification of Reduced Dynamic Models of Barge-Type Floating Wind Turbines." Energies 14, no. 13 (June 29, 2021): 3902. http://dx.doi.org/10.3390/en14133902.
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Floating offshore wind turbines (FOWT) are designed to overcome some of the limitations of offshore bottom-fixed ones. The development of computational models to simulate the behavior of the structure and the turbine is key to understanding the wind energy system and demonstrating its feasibility. In this work, a general methodology for the identification of reduced dynamic models of barge-type FOWTs is presented. The method is described together with an example of the development of a dynamic model of a 5 MW floating offshore wind turbine. The novelty of the proposed identification methodology lies in the iterative loop relationship between the identification and validation processes. Diversified data sets are used to select the best-fitting identified parameters by cross evaluation of every set among all validating conditions. The data set is generated for different initial FOWT operating conditions. Indeed, an optimal initial condition for platform pitch was found to be far enough from the system at rest to allow the dynamics to be well characterized but not so far that the unmodeled system nonlinearities were so large that they affected significantly the accuracy of the model. The model has been successfully applied to structural control research to reduce fatigue on a barge-type FOWT.
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Liu, Baolong, and Jianxing Yu. "Effect of Mooring Parameters on Dynamic Responses of a Semi-Submersible Floating Offshore Wind Turbine." Sustainability 14, no. 21 (October 27, 2022): 14012. http://dx.doi.org/10.3390/su142114012.
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Based on a new semi-submersible floating offshore wind turbine (FOWT), a coupling aero-hydro-flexible model was established to study its dynamic behaviors, as well as the corresponding mooring system, under complicated sea scenarios. The aerodynamic load, the wave load, the current load, and the mooring load were taken into consideration. To further investigate the influence of the mooring parameters on the floating system, the diameter and the total length of mooring lines, which are the most critical parameters in mooring line design, were chosen to be analyzed. Particularly, five diameters and seven lengths were adopted to establish the FOWT mooring system, and a time-domain simulation was carried out for each cases. Based on the numerical simulations, their influences on the mooring system stiffness and the dynamic responses of FOWT were studied. The results show that the diameter has little influence on the static shape of the mooring line. The mooring system stiffness can be effectively increased by reducing the length and increasing the diameter of mooring lines. Moreover, the surge motion of floating foundation can be effectively controlled by increasing the mooring line diameter and decreasing mooring line length under the rated sea scenario. From this aspect, the dynamic response features of the FOWTs could be improved.
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Belvasi, Navid, Frances Judge, Jimmy Murphy, and Cian Desmond. "Analysis of Floating Offshore Wind Platform Hydrodynamics Using Underwater SPIV: A Review." Energies 15, no. 13 (June 24, 2022): 4641. http://dx.doi.org/10.3390/en15134641.
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There is a need for new numerical tools to capture the physics of floating offshore wind turbines (FOWTs) more accurately to refine engineering designs and reduce costs. The conventional measurement apparatuses in tank tests, including wave probes, velocity and current profilers, and Doppler sensors, are unable to provide a full 3D picture of velocity, pressure, turbulence, and vorticity profile. In tank tests, use of the underwater stereoscopic particle image velocimetry (SPIV) method to fully characterise the 3D flow field around floating wind platforms can overcome some of the limitations associated with classical measurement techniques and provide a rich source of validation data to advance high-fidelity numerical tools. The underwater SPIV method has been widely used for marine and offshore applications, including ship and propeller wakes, wave dynamics, and tidal stream turbines; however, to date, this technology has not seen widespread use for the hydrodynamic study of FOWTs. This paper provides a critical review of the suitability of underwater SPIV for analysing the hydrodynamics of FOWTs, reviews the challenges of using the method for FOWT tank test applications, and discusses the contributions the method can make to mitigating current research gaps in FOWT tank tests.
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Zhai, Yuting, Haisheng Zhao, Xin Li, and Wei Shi. "Design and Dynamic Analysis of a Novel Large-Scale Barge-Type Floating Offshore Wind Turbine with Aquaculture Cage." Journal of Marine Science and Engineering 10, no. 12 (December 6, 2022): 1926. http://dx.doi.org/10.3390/jmse10121926.
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In this study, a novel large-scale barge-type floating offshore wind turbine with an aquaculture cage (LSBT-FOWT-AC) in a water depth of 100 m is designed through fully coupled analysis using the SESAM tool to support the Technical University of Denmark (DTU) 10 MW wind turbine. The intact stability and natural period of motion of the newly designed LSBT-FOWT-AC are evaluated based on the DNV rules and standards. Then, the dynamic responses of the LSBT-FOWT-AC under various sea conditions are studied. The motion of the LSBT-FOWT-AC platform is considerably affected by waves, and its motion response is within a reasonable range even under the extreme sea conditions of the 100-year return period. By analyzing the results of the out-of-plane bending moment of root of blade 1 (RootMyc1), it can be seen that the rotor frequency (1P) has a visible influence on the wind turbine. Through the analysis of dynamic response statistics of the LSBT-FOWT-AC structure by the single variable method of environmental loads, it is found that wind force exerts the greatest impact on the dynamic response compared to the wave-excitation force and current drag force.
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Wu, Hai Tao, Jin Jiang, Jing Zhao, and Xiao Rong Ye. "Dynamic Response of a Semi-Submersible Floating Offshore Wind Turbine in Storm Condition." Applied Mechanics and Materials 260-261 (December 2012): 273–78. http://dx.doi.org/10.4028/www.scientific.net/amm.260-261.273.
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The paper focuses on a semi-submersible floating offshore wind turbine (FOWT) and analyses its dynamic response in storm condition. The wind load is calculated based on wind block model; the hydrodynamic load is modeled using Potential Theory and Morison Equation. The time-domain dynamic response of the FOWT is simulated by SESAM software with duration of 3 hours. The performance of the FOWT is analyzed based on time history responses and response spectrums. The results show some unique characteristics that differ from offshore platforms and the analysis proofs that the performance is acceptable and the design is reliable.
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Zheng, Xiang, and Yu Lei. "Stochastic Response Analysis for a Floating Offshore Wind Turbine Integrated with a Steel Fish Farming Cage." Applied Sciences 8, no. 8 (July 26, 2018): 1229. http://dx.doi.org/10.3390/app8081229.
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A state-of-the-art concept integrating a deepwater floating offshore wind turbine with a steel fish-farming cage (FOWT-SFFC) is presented in this paper. The configurations of this floating structure are given in detail, showing that the multi-megawatt wind turbine sitting on the cage foundation possesses excellent hydrostatic stability. The motion response amplitude operators (RAOs) calculated by the potential-flow program WAMIT demonstrate that the hydrodynamic performance of FOWT-SFFC is much better than OC3Hywind spar and OC4DeepCwind semisubmersible wind turbines. The aero-hydro-servo-elastic modeling and time-domain simulations are carried out by FAST to investigate the dynamic response of FOWT-SFFC for several environmental conditions. The short-term extreme stochastic response reveals that the dynamic behavior of FOWT-SFFC outperforms its counterparts. From the seakeeping and structural dynamic views, it is a very competitive and promising candidate in offshore industry for both power exploitation and aquaculture in deep waters.
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Zhou, Yiming, Yajun Ren, Wei Shi, and Xin Li. "Investigation on a Large-Scale Braceless-TLP Floating Offshore Wind Turbine at Intermediate Water Depth." Journal of Marine Science and Engineering 10, no. 2 (February 21, 2022): 302. http://dx.doi.org/10.3390/jmse10020302.
Full textAbstract:
Tension leg platform (TLP) is a cost-effective and high-performance support structure for floating offshore wind turbine (FOWT) because of its small responses in heave, pitch, and roll with the constraint of the tendons. China, as the largest market of offshore wind energy, has shown a demand for developing reliable, viable floating platform support structures, especially aiming at the intermediate water depth. The present paper described a newly proposed 10-MW Braceless-TLP FOWT designed for a moderate water depth of 60 m. The numerical simulations of the FOWT are carried out using the coupled aero-hydro-servo-elastic-mooring calculation tool FAST. The measured wind and wave data of the target site close to the Fujian Province of China were used to evaluate the performance of the FOWT under the 100-, 50-, 5-, and 2-year-return stochastic weather conditions. The natural periods of the platform in surge, sway, heave, pitch, roll, and yaw were found to be within the range recommended by the design standard DNV-RP-0286 Coupled Analysis of Floating Wind Turbines. The largest surge of the water depth ratio among all the load cases was 15%, which was smaller than the admissible ratio of 23%. The tower top displacements remained between −1 m and 1 m, which were at a similar order to those of a 10-MW monopile-supported offshore wind turbine. The six tendons remained tensioned during the simulation, even under the operational and extreme (parked) environmental conditions. The Braceless-TLP FOWT showed an overall satisfying performance in terms of the structural stability and illustrates the feasibility of this type of FOWT at such a moderate water depth.
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Suzuki, Hideyuki, Hiroki Shiohara, Anja Schnepf, Hidetaka Houtani, Lucas H. S. Carmo, Shinichiro Hirabayashi, Ken Haneda, et al. "Wave and Wind Responses of a Very-Light FOWT with Guy-Wired-Supported Tower: Numerical and Experimental Studies." Journal of Marine Science and Engineering 8, no. 11 (October 26, 2020): 841. http://dx.doi.org/10.3390/jmse8110841.
Full textAbstract:
A floating offshore wind turbine (FOWT) concept with a guy-wire-supported tower was investigated to obtain motion results in waves considering its elastic model characteristics. The FOWT concept studied aims to reduce the construction costs by using a light-weight structure tensioned with guy wires and a downwind type. Wave tank experiments of an elastically similar segmented backbone model in the 1:60 scale were carried out to clarify the dynamic elastic response features of the structure. The experimental results were compared with numerical simulations obtained from NK-UTWind and WAMIT codes. The bending moment measured at the tower and pontoons had two peak values for different wave periods carried out. The short-wave period peak was due to sagging/hogging when the wavelength matched the floater length. The second peak was due to the large tower top acceleration, which caused a large bending moment at the tower base and pontoon to support the inertia force. The wind force was not significant to modify the FOWT response. The sensibility analysis in pontoons and tower rigidities confirmed the importance of the guy wires to support the inertia due to the waves and wind incidence. The new concept of a very-light FOWT with a guy-wire-supported tower may be an option for future FOWT developments.
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Zhao, Zhixin, Xin Li, Wenhua Wang, and Wei Shi. "Analysis of Dynamic Characteristics of an Ultra-Large Semi-Submersible Floating Wind Turbine." Journal of Marine Science and Engineering 7, no. 6 (June 1, 2019): 169. http://dx.doi.org/10.3390/jmse7060169.
Full textAbstract:
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.
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Lei, Y., S. X. Zhao, X. Y. Zheng, and W. Li. "Effects of Fish Nets on the Nonlinear Dynamic Performance of a Floating Offshore Wind Turbine Integrated with a Steel Fish Farming Cage." International Journal of Structural Stability and Dynamics 20, no. 03 (March 2020): 2050042. http://dx.doi.org/10.1142/s021945542050042x.
Full textAbstract:
This paper aims to study the effects of fish nets on the nonlinear dynamic performance of a floating offshore wind turbine integrated with a steel fish farming cage (FOWT-SFFC). Fully coupled aero-hydro-servo-elastic numerical models of FOWT-SFFC, with and without nets, are constructed to probe the nonlinear time-domain stochastic response. The first-order potential flow model with quadratic drag forces is employed to calculate the hydrodynamic loading on the foundation. The effects of nets on the damping ratios of 6 degree-of-freedom motions and on their displacement response amplitude operators (RAOs) are respectively investigated in numerical decay tests and monochromatic regular waves. The results show that the nets help to increase the damping level for the whole system and reduce motion RAOs when wave periods are around the natural periods of motions, while nets play insignificant role in motions when wave periods are far away from motion natural periods. The dynamic performances of FOWT-SFFC with and without nets under random ocean waves, the combined random wind and random waves as well as current are comprehensively compared and discussed. The simulation results indicate that in wind-sea dominated conditions, the nets tend to slightly increase the dynamic responses of FOWT-SFFC, especially the components corresponding to natural periods. Nonetheless, under sea states that comprise both wind-sea waves and swell, nets help to reduce the dynamic responses of FOWT-SFFC by introducing additional damping.
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Kosasih, Ko Matias Adrian, Hideyuki Suzuki, Hideyuki Niizato, and Shigeki Okubo. "Demonstration Experiment and Numerical Simulation Analysis of Full-Scale Barge-Type Floating Offshore Wind Turbine." Journal of Marine Science and Engineering 8, no. 11 (November 5, 2020): 880. http://dx.doi.org/10.3390/jmse8110880.
Full textAbstract:
The development of Floating Offshore Wind Turbines (FOWT) has been progressing steadily. To utilize the moderate water depth of 50–100 m ocean space around Japan, a barge-type FOWT was installed in Kitakyushu as part of a demonstration project conducted by the New Energy and Industrial Technology Development Organization (NEDO) of Japan. The FOWT mounts a 3 MW two-bladed wind turbine with blade diameter of 100 m and hub height of 72 m. The barge-type floating support structure is equipped with a moonpool in the center and a skirt at its bottom and is moored with 9 lines of catenary chains. To investigate the dynamic behavior of the barge-type FOWT in extreme condition and the validity of the numerical simulation in modeling the effect of the complex flow around the floating structure to the FOWT’s motion response, the FOWT’s motion data during typhoon Tapah on 23 September 2019 were measured and compared with the simulation results. As the results, the simulation results showed a good agreement in general to the measurement data. However, some shifts in the peak frequency of the simulation’s motion spectrum and a disagreement in waves with shorter wave periods were also observed. The possible causes of these differences are discussed thoroughly in this paper.
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Ramos, Roberto. "Linear Quadratic Optimal Control of a Spar-Type Floating Offshore Wind Turbine in the Presence of Turbulent Wind and Different Sea States." Journal of Marine Science and Engineering 6, no. 4 (December 7, 2018): 151. http://dx.doi.org/10.3390/jmse6040151.
Full textAbstract:
This paper presents the design of a linear quadratic (LQ) optimal controller for a spar-type floating offshore wind turbine (FOWT). The FOWT is exposed to different sea states and constant wind turbulence intensity above rated wind speed. A new LQ control objective is specified for the floater-turbine coupled control, in accordance with standard requirements, to reduce both rotor speed fluctuations and floater pitch motion in each relevant sea state compared with a baseline proportional-integral (PI) controller. The LQ weighting matrices are selected using time series of the wind/wave disturbances generated for the relevant sea states. A linearized state-space model is developed, including the floater surge/pitch motions, rotor speed, collective blade pitch actuation, and unmeasured environmental disturbances. The wind disturbance modeling is based on the Kaimal spectrum and aerodynamic thrust/torque coefficients. The wave disturbance modeling is based on the Pierson–Moskowitz spectrum and linearized Morison equation. A high-fidelity FOWT simulator is used to verify the control-oriented model. The simulation results for the OC3-Hywind FOWT subjected to turbulent wind show that a single LQ controller can yield both rotor speed fluctuation reduction of 32–72% and floater pitch motion reduction of 22–44% in moderate to very rough sea states compared with the baseline PI controller.
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Huang, Yang, and Decheng Wan. "Investigation of Interference Effects Between Wind Turbine and Spar-Type Floating Platform Under Combined Wind-Wave Excitation." Sustainability 12, no. 1 (December 27, 2019): 246. http://dx.doi.org/10.3390/su12010246.
Full textAbstract:
In order to further understand the coupled aero-hydrodynamic performance of the floating offshore wind turbine (FOWT) in realistic ocean environment, it is necessary to investigate the interference effects between the unsteady aerodynamics of the wind turbine and different degree-of-freedom (DOF) platform motions under combined wind-wave excitation. In this paper, a validated CFD analysis tool FOWT-UALM-SJTU with modified actuator line model is applied for the coupled aero-hydrodynamic simulations of a spar-type FOWT system. The aero-hydrodynamic characteristics of the FOWT with various platform motion modes and different wind turbine states are compared and analyzed to explore the influence of the interference effects between the wind turbine and the floating platform on the performance of the FOWT. The dynamic responses of local relative wind speed and local attack angle at the blade section and wind-wave forces acting on the floating platform are discussed in detail to reveal the interaction mechanism between the aerodynamic loads and different DOF platform motions. It is shown that the surge motion and the pitch motion of the floating platform both significantly alter the local attack angle, while only the platform pitch motion have significant impacts on the local relative wind speed experienced by the rotating blades. Besides, the shaft tilt and the pro-cone angle of the wind turbine and the height-dependent wind speed all contribute to the variation of the local attack angle. The coupling between the platform motions along different DOFs is obviously amplified by the aerodynamic forces derived from the wind turbine. In addition, the wake deflection phenomenon is clearly observed in the near wake region when platform pitch motion is considered. The dynamic pitch motion of the floating platform also contributes to the severe wake velocity deficit and the increased wake width.
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Liu, Baolong, and Jianxing Yu. "Dynamic Response of SPAR-Type Floating Offshore Wind Turbine under Wave Group Scenarios." Energies 15, no. 13 (July 2, 2022): 4870. http://dx.doi.org/10.3390/en15134870.
Full textAbstract:
Numerical simulations are performed within the time domain to investigate the dynamic behaviors of an SPAR-type FOWT under wave group conditions. Towards this goal, the OC3 Hywind SPAR-type FOWT is adopted, and a JONSWAP (Joint North Sea Wave Project)-based wave group is generated by the envelope amplitude approach. The FOWT motion under wave group conditions, as well as the aerodynamic, hydrodynamic, and mooring performances, is simulated by our established in-house code. The rotating blades are modelled by the blade element momentum theory. The wave-body interaction effect is calculated by the three-dimensional potential theory. The mooring dynamics are also taken into consideration. According to the numerical results, the SPAR buoy motions are slightly increased by the wave group, while the heave motion is significantly amplified. Both the aerodynamic performance and the mooring tension are also influenced by the wave group. Furthermore, the low-frequency resonant response could be more easily excited by the wave group.
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Sivalingam, Krishnamoorthi, Steven Martin, and Abdulqadir Singapore Wala. "Numerical Validation of Floating Offshore Wind Turbine Scaled Rotors for Surge Motion." Energies 11, no. 10 (September 27, 2018): 2578. http://dx.doi.org/10.3390/en11102578.
Full textAbstract:
Aerodynamic performance of a floating offshore wind turbine (FOWT) is significantly influenced by platform surging motions. Accurate prediction of the unsteady aerodynamic loads is imperative for determining the fatigue life, ultimate loads on key components such as FOWT rotor blades, gearbox and power converter. The current study examines the predictions of numerical codes by comparing with unsteady experimental results of a scaled floating wind turbine rotor. The influence of platform surge amplitude together with the tip speed ratio on the unsteady aerodynamic loading has been simulated through unsteady CFD. It is shown that the unsteady aerodynamic loads of FOWT are highly sensitive to the changes in frequency and amplitude of the platform motion. Also, the surging motion significantly influences the windmill operating state due to strong flow interaction between the rotating blades and generated blade-tip vortices. Almost in all frequencies and amplitudes, CFD, LR-BEM and LR-uBEM predictions of mean thrust shows a good correlation with experimental results.
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Wu, Hai Tao, Liang Zhang, Jing Zhao, and Xiao Rong Ye. "Primary Design and Dynamic Analysis of an Articulated Floating Offshore Wind Turbine." Advanced Materials Research 347-353 (October 2011): 2191–94. http://dx.doi.org/10.4028/www.scientific.net/amr.347-353.2191.
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The paper focuses on floating offshore wind turbine (FOWT) and makes a review of famous designs. FOWT foundation is classified into three categories based on the strategy to achieve static stability. In order for utilization, a new concept is proposed and primary design for water depth of 90m is described. Moreover, dynamic analysis of this concept under operational condition is carried out. The thrust force on the rotor is evaluated based on software analysis; the hydrodynamic forces are calculated using Morison equation. The results indicate that the concept is excellent and worth for further development.
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Liu, Xiaolei, and Motohiko Murai. "Engineering Possibility Studies of a Novel Cylinder-Type FOWT Using Torus Structure with Annular Flow." Energies 15, no. 13 (July 5, 2022): 4919. http://dx.doi.org/10.3390/en15134919.
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This paper proposes and researches a novel cylinder-type FOWT using a neutrally buoyant double-layer torus structure with annular flow; its oscillatory motion in severe sea conditions is controlled by a spinning top device designed as a neutrally buoyant double-layer torus structure with annular flow water in a torus structure with a small internal radius, and welded to the periphery of the cylinder-type FOWT underwater buoyancy-providing part. The rotational axis retention effect and the gyroscopic effect are considered appropriate approaches to suppress the oscillating motion of FOWT. To obtain a better hydrodynamic response, the scale of the torus structure, such as its radius, the radius of the internal annular flow water, and the angular velocity of the annular flow water are taken as the design parameters, and a large number of comparative calculations based on the fluid–solid coupling theory of potential flow are carried out to determine the appropriate design parameters. Eventually, on the basis of the obtained suitable design parameters, the proposed conceptual design approach is demonstrated to be feasible in view of the energy consumption.
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Wang, H. F., and Y. H. Fan. "Spoke Dimension on the Motion Performance of a Floating Wind Turbine with Tension-Leg Platform." Shock and Vibration 2016 (2016): 1–16. http://dx.doi.org/10.1155/2016/8913873.
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The tension-leg platform (TLP) supporting structure is a good choice for floating offshore wind turbines because TLP has superior motion dynamics. This study investigates the effects of TLP spoke dimensions on the motion of a floating offshore wind turbine system (FOWT). Spoke dimension and offshore floating TLP were subjected to irregular wave and wind excitation to evaluate the motion of the FOWT. This research has been divided into two parts: (1) Five models were designed based on different spoke dimensions, and aerohydroservo-elastic coupled analyses were conducted on the models using the finite element method. (2) Considering the coupled effects of the dynamic response of a top wind turbine, a supporting-tower structure, a mooring system, and two models on a reduced scale of 1 : 80 were constructed and experimentally tested under different conditions. Numerical and experimental results demonstrate that the spoke dimensions have a significant effect on the motion of FOWT and the experimental result that spoke dimension can reduce surge platform movement to improve turbine performance.
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Bashir, Musa, Zifei Xu, Jin Wang, and C. Guedes Soares. "Data-Driven Damage Quantification of Floating Offshore Wind Turbine Platforms Based on Multi-Scale Encoder–Decoder with Self-Attention Mechanism." Journal of Marine Science and Engineering 10, no. 12 (November 29, 2022): 1830. http://dx.doi.org/10.3390/jmse10121830.
Full textAbstract:
A Multi-Scale Convolutional Neural Network with Self Attention-based Auto Encoder–Decoder (MSCSA-AED), is a novel high-performance framework, presented here for the quantification of damage on a multibody floating offshore wind turbine (FOWT) structure. The model is equipped with similarity measurement to enhance its capability to accurately quantify damage effects from different scales of coded features using raw platform responses and without human intervention. Case studies using different damage magnitudes on tendons of a 10 MW multibody FOWT were used to examine the accuracy and reliability of the proposed model. The results showed that addition of Square Euclidean (SE) distance enhanced the MSCSA-AED model’s capability to suitably estimate the damage in structures operating in complex environments using only raw responses. Comparison of the model’s performance with other variants (DCN-AED and MSCNN-AED) used in the industry to extract the coded features from FOWT responses further demonstrated the superiority of MSCSA-AED in complex operating conditions, especially in low magnitude damage quantification, which is the hardest to quantify.
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M’zoughi, Fares, Izaskun Garrido, Aitor J. Garrido, and Manuel De La Sen. "Fuzzy Airflow-Based Active Structural Control of Integrated Oscillating Water Columns for the Enhancement of Floating Offshore Wind Turbine Stabilization." International Journal of Energy Research 2023 (February 7, 2023): 1–23. http://dx.doi.org/10.1155/2023/4938451.
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This paper presents the modeling and stabilization of a floating offshore wind turbine (FOWT) using oscillating water columns (OWCs) as active structural control. The novel concept of this work is to design a new FOWT platform using the ITI Energy barge with incorporated OWCs at opposite sides of the tower, in order to alleviate the unwanted system oscillations. The OWCs provide the necessary opposing forces to the bending moment of the wind upon the tower and the waves upon the floating barge platform. However, the forces have to be synchronized with the tilting of the system which will be ensured by the proposed fuzzy airflow control strategy. Using the platform pitch angle, the fuzzy airflow control opens the valve of one side and closes the valve of the other side accordingly. Results of simulation in comparison with the standard FOWT and a PID-based airflow control show the efficiency of the fuzzy airflow control and its superiority to decrease the platform pitching and the top tower fore-aft displacement.
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Iwamatsu, Saika, Hideyuki Suzuki, and Yasunori Nihei. "Study on Elastic Response of Double-Roter VAWTs." Journal of Marine Science and Engineering 10, no. 10 (September 30, 2022): 1400. http://dx.doi.org/10.3390/jmse10101400.
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This study investigates the elastic response characteristics of a floating wind turbine (FOWT) with two vertical-axis wind turbines (VAWTs), called double-rotor VAWTs. The model consists of two VAWTs mounted on a single semi-submersible floating structure and employs a single point mooring, which allows the FOWT to always self-align with the wind. Usually, a coupled analysis of the wind turbine and floating structure is used in the design of FOWTs; however, there is no coupled analysis available for VAWTs. In this study, we attempted to combine the wind turbine design software “QBlade” and the coupled wind turbine/floating body analysis code “UTWind” as one of the methods of coupled analysis of a VAWT and a floating body. Numerical simulation results were compared with experimental results using an elastic model scaled down to 1/100 of its actual model to determine the motion response and cross-sectional bending moments. The experimental results showed that the thrust of the VAWT had a particular influence on the cross-sectional forces and motion response between the two VAWTs. For cross-sectional forces, all results showed similar trends. Overall, the results of UTWind for double-rotor VAWTs are reasonable. It was also found that the pitch motion must be accurately reproduced to improve the accuracy.
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Elkafas, Ahmed G., Yasser M. Ahmed, and Mohamed M. Elgohary. "Hydrodynamic Analysis of Floating Offshore Wind Turbine With Different Numbers of Offset Columns." Marine Technology Society Journal 56, no. 2 (April 27, 2022): 8–19. http://dx.doi.org/10.4031/mtsj.56.2.1.
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Abstract Currently, there is a strong interest to develop offshore wind energy because of the great impact of greenhouse gases and the energy crisis. Extraordinary endeavors have been dedicated to creating floating offshore wind turbine (FOWT) innovations such as the DeepCwind semi-submersible FOWT that can be relied upon to harness wind energy in deep water. However, DeepCwind structure faces a significant surge motion limiting the operational time. Therefore, this paper presents three different configurations for the DeepCwind semi-submersible FOWT by varying the number of offset columns from three to five columns to improve the wave resistance ability. Hydrodynamic analysis is carried out to figure and compare the performance of these platforms via the ANSYS-AQWA tool. The free-decay test has shown that the natural frequency is affected by the number of offset columns. The results of statistics on regular waves and irregular waves have shown that the surge response is inversely proportional to the number of offset columns; the statistics decrease with the increase of the offset columns number, while the impacts of increasing offset columns are negligible for the heave and pitch motions.
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Pham, Thanh-Dam, and Hyunkyoung Shin. "The Effect of the Second-Order Wave Loads on Drift Motion of a Semi-Submersible Floating Offshore Wind Turbine." Journal of Marine Science and Engineering 8, no. 11 (October 30, 2020): 859. http://dx.doi.org/10.3390/jmse8110859.
Full textAbstract:
Floating offshore wind turbines (FOWTs) have been installed in Europe and Japan with relatively modern technology. The installation of floating wind farms in deep water is recommended because the wind speed is stronger and more stable. The design of the FOWT must ensure it is able to withstand complex environmental conditions including wind, wave, current, and performance of the wind turbine. It needs simulation tools with fully integrated hydrodynamic-servo-elastic modeling capabilities for the floating offshore wind turbines. Most of the numerical simulation approaches consider only first-order hydrodynamic loads; however, the second-order hydrodynamic loads have an effect on a floating platform which is moored by a catenary mooring system. At the difference-frequencies of the incident wave components, the drift motion of a FOWT system is able to have large oscillation around its natural frequency. This paper presents the effects of second-order wave loads to the drift motion of a semi-submersible type. This work also aimed to validate the hydrodynamic model of Ulsan University (UOU) in-house codes through numerical simulations and model tests. The NREL FAST code was used for the fully coupled simulation, and in-house codes of UOU generates hydrodynamic coefficients as the input for the FAST code. The model test was performed in the water tank of UOU.
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Pan, Qi, and Po Wen Cheng. "Cost-based mooring designs and a parametric study of bridles for a 15 MW spar-type floating offshore wind turbine." Journal of Physics: Conference Series 2265, no. 4 (May 1, 2022): 042013. http://dx.doi.org/10.1088/1742-6596/2265/4/042013.
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Abstract This paper highlights a cost-based design method for feasible and cost-effective mooring configurations. A parametric study of mooring designs considering bridle impact is performed for a 15 MW spar-type floating offshore wind turbine (FOWT). This site-specific FOWT is based on the preliminary model from EU funded H2020 Project COREWIND. Without running numerical simulations, the cost-based design method generates 1443 mooring configurations with normalized costs ranging from 1.00 to 1.667. Six configurations with the lowest normalized costs are selected for OpenFAST simulations. The ultimate test results verify the structural strength of mooring configurations. Bridle designs cause significant impact on the ultimate mooring tensions and floater motions in surge, sway and yaw, which is clearly influenced by the mass ratio of a bridle to a mooring line. When the mass ratio decreases from 13% to 5%, peak mooring tensions increase by up to 17%. The influence of bridle designs on mooring tension fatigue is less prominent and the effect of mass ratio on mooring fatigue varies with wind speed. Near the rated wind speed, deviations in mooring fatigue loads are within 5% for all six configurations. This cost-based method promotes feasible and economical mooring designs. The parametric study of bridle designs provides solid support for optimal mooring designs of spar-type FOWTs.
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Serrano, Carlos, Jesus-Enrique Sierra-Garcia, and Matilde Santos. "Hybrid Optimized Fuzzy Pitch Controller of a Floating Wind Turbine with Fatigue Analysis." Journal of Marine Science and Engineering 10, no. 11 (November 17, 2022): 1769. http://dx.doi.org/10.3390/jmse10111769.
Full textAbstract:
Floating offshore wind turbines (FOWTs) are systems with complex and highly nonlinear dynamics; they are subjected to heavy loads, making control with classical strategies a challenge. In addition, they experience vibrations due to wind and waves. Furthermore, the control of the blade angle itself may generate vibrations. To address this issue, in this work we propose the design of an intelligent control system based on fuzzy logic to maintain the rated power of an FOWT while reducing the vibrations. A gain scheduling incremental proportional–derivative fuzzy controller is tuned by genetic algorithms (GAs) and combined with a fuzzy-lookup table to generate the pitch reference. The control gains optimized by the GA are stored in a database to ensure a proper operation for different wind and wave conditions. The software Matlab/Simulink and the simulation tool FAST are used. The latter simulates the nonlinear dynamics of a real 5 MW barge-type FOWT with irregular waves. The hybrid control strategy has been evaluated against the reference baseline controller embedded in FAST in different environmental scenarios. The comparison is assessed in terms of output power and structure stability, with up to 23% and 33% vibration suppression rate for tower top displacement and platform pitch, respectively, with the new control scheme. Fatigue damage equivalent load (DEL) of the blades has been also estimated with satisfactory results.
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Mei, Xuan, and Min Xiong. "Effects of Second-Order Hydrodynamics on the Dynamic Responses and Fatigue Damage of a 15 MW Floating Offshore Wind Turbine." Journal of Marine Science and Engineering 9, no. 11 (November 7, 2021): 1232. http://dx.doi.org/10.3390/jmse9111232.
Full textAbstract:
In order to investigate the effects of second-order hydrodynamic loads on a 15 MW floating offshore wind turbine (FOWT), this study employs a tool that integrates AQWA and OpenFAST to conduct fully coupled simulations of the FOWT subjected to wind and wave loadings. The load cases covering normal and extreme conditions are defined based on the met-ocean data observed at a specific site. The results indicate that the second-order wave excitations activate the surge mode of the platform. As a result, the surge motion is increased for each of the examined load case. In addition, the pitch, heave, and yaw motions are underestimated when neglecting the second-order hydrodynamics under the extreme condition. First-order wave excitation is the major contributor to the tower-base bending moments. The fatigue damage of the tower-base under the extreme condition is underestimated by 57.1% if the effect of second-order hydrodynamics is ignored. In addition, the accumulative fatigue damage over 25 years at the tower-base is overestimated by 16.92%. Therefore, it is suggested to consider the effects of second-order wave excitations of the floating platform for the design of the tower to reduce the cost of the FOWT.
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Lerch, Markus, Mikel De-Prada-Gil, and Climent Molins. "A simplified model for the dynamic analysis and power generation of a floating offshore wind turbine." E3S Web of Conferences 61 (2018): 00001. http://dx.doi.org/10.1051/e3sconf/20186100001.
Full textAbstract:
This paper presents a simplified model for the dynamic analysis of a floating off-shore wind turbine (FOWT), which can be suitable for early feasibility and pre-engineering studies, where the complete system has to modeled in order to predict its behavior and to assess the performance. The model solves the equation of motion in time domain and considers Morison equation for computing the hydrodynamic loads. The aerodynamic loads are included by considering the wind thrust at hub height and the loads from the mooring system have been computed as a non-linear model. A methodology is also presented for calculating the structural properties of the system. The model is tested for two load cases and compared to results obtained with the more complex model FAST. The comparison between the response of the models is satisfactory. The simplified model allows to capture the main motions of the FOWT with an acceptable accuracy. A further feature of the model is to calculate the power generation of the floating wind turbine. The results show that the losses in comparison with a bottom-fixed off-shore wind turbine are below 1% or 1.1% according to the load case, which confirms the good performance of the studied FOWT.
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Youssef Mahfouz, Mohammad, Matthew Hall, and Po Wen Cheng. "A parametric study of the mooring system design parameters to reduce wake losses in a floating wind farm." Journal of Physics: Conference Series 2265, no. 4 (May 1, 2022): 042004. http://dx.doi.org/10.1088/1742-6596/2265/4/042004.
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Abstract Wake effects inside a conventional fixed bottom wind farm decrease the power produced by the downwind turbines, hence decreasing the farm’s annual energy production (AEP). However, floating offshore wind turbines (FOWTs) have the ability to relocate their positions laterally through surge and sway motions. This flexibility provides a new degree of freedom (DOF) in the floating wind farm layout, which can be used to decrease the aerodynamic interactions inside the floating wind farm and hence decrease the wake losses. The lateral movement of FOWTs can be passively controlled by the mooring system design. The mooring system’s restoring characteristics allows the FOWT to only move within a specific area in the x-y plane known as the watch circle. Current state of the art mooring system designs are following oil and gas design basis where the floating platforms are not allowed to have large lateral displacements. In this work, we use full factorial design to analyse the effect of different mooring system design parameters on the ability of the floater to relocate its position. The analysis shows that each design parameter has a different way of affecting the FOWT’s response. The mooring lines’ headings control which wind directions cause the biggest displacements in the crosswind direction. The smaller the lines’ diameters the higher the displacements of the FOWT. Finally, the longer the line length the smaller the mooring system’s stiffness and hence the larger the FOWT’s displacement. The results of this study can be used as the basis for floating wind farm optimization, in which the wind turbines are allowed to passively relocate their positions according to the wind speed and wind direction.
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Takata, Taisuke, Mayuko Takaoka, Hidetaka Houtani, Kentaro Hara, Sho Oh, Edgard B. Malta, Kazuhiro Iijima, Hideyuki Suzuki, and Rodolfo T. Gonçalves. "Effect of Heave Plates on the Wave Motion of a Flexible Multicolumn FOWT." Energies 15, no. 20 (October 14, 2022): 7605. http://dx.doi.org/10.3390/en15207605.
Full textAbstract:
Three models with different footing types were used to clarify the effect of heave plates on the hydrodynamic behavior of the elastic response of a flexible multicolumn floating offshore wind turbine (FOWT). The models were tested under regular waves, whose added mass, damping, and motion response results were compared with numerical simulations by NK-UTWind and WAMIT codes. As a whole, the attachment of heave plates was responsible for increasing the added mass and damping levels, consequently modifying the RAO of the models. Regarding the response in a sea condition, a decrease of 33% and 66% of the significant motion height (heave and pitch) was observed. Thus, the heave plate can be a good feature for the future design of FOWT.
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Manolas, Dimitris I., Vasilis A. Riziotis, George P. Papadakis, and Spyros G. Voutsinas. "Hydro-Servo-Aero-Elastic Analysis of Floating Offshore Wind Turbines." Fluids 5, no. 4 (November 5, 2020): 200. http://dx.doi.org/10.3390/fluids5040200.
Full textAbstract:
A fully coupled hydro-servo-aero-elastic simulator for the analysis of floating offshore wind turbines (FOWTs) is presented. All physical aspects are addressed, and the corresponding equations are concurrently solved within the same computational framework, taking into account the wind and wave excitations, the aerodynamic response of the rotor, the hydrodynamic response of the floater, the structural dynamics of the turbine-floater-mooring lines assembly and finally the control system of the wind turbine. The components of the complex multi-physics system of a FOWT interact with each other in an implicitly coupled manner leading to a holistic type of modeling. Different modeling options, of varying fidelity and computational cost, are made available with respect to rotor aerodynamics, hydrodynamic loading of the floater and mooring system dynamics that allow for timely routine certification simulations, but also for computationally intense simulations of less conventional operating states. Structural dynamics is based on nonlinear multibody analysis that allows reproducing the large rigid body motions undergone by the FOWT, as well as large deflections and rotations of the highly flexible blades. The paper includes the description of the main physical models, of the interaction and solution strategy and representative results. Verification is carried out by comparing with other state-of-art tools that participated in the Offshore Code Comparison Collaboration Continuation (OC4) IEA Annex, while the advanced simulation capabilities are demonstrated in the case of half-wake interaction of floating wind turbines by employing the free-wake aerodynamic method.
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Zhang, Yin, and Bumsuk Kim. "A Fully Coupled Computational Fluid Dynamics Method for Analysis of Semi-Submersible Floating Offshore Wind Turbines Under Wind-Wave Excitation Conditions Based on OC5 Data." Applied Sciences 8, no. 11 (November 20, 2018): 2314. http://dx.doi.org/10.3390/app8112314.
Full textAbstract:
Accurate prediction of the time-dependent system dynamic responses of floating offshore wind turbines (FOWTs) under aero-hydro-coupled conditions is a challenge. This paper presents a numerical modeling tool using commercial computational fluid dynamics software, STAR-CCM+(V12.02.010), to perform a fully coupled dynamic analysis of the DeepCwind semi-submersible floating platform with the National Renewable Engineering Lab (NREL) 5-MW baseline wind turbine model under combined wind–wave excitation environment conditions. Free-decay tests for rigid-body degrees of freedom (DOF) in still water and hydrodynamic tests for a regular wave are performed to validate the numerical model by inputting gross system parameters supported in the Offshore Code Comparison, Collaboration, Continued, with Correlations (OC5) project. A full-configuration FOWT simulation, with the simultaneous motion of the rotating blade due to 6-DOF platform dynamics, was performed. A relatively heavy load on the hub and blade was observed for the FOWT compared with the onshore wind turbine, leading to a 7.8% increase in the thrust curve; a 10% decrease in the power curve was also observed for the floating-type turbines, which could be attributed to the smaller project area and relative wind speed required for the rotor to receive wind power when the platform pitches. Finally, the tower-blade interference effects, blade-tip vortices, turbulent wakes, and shedding vortices in the fluid domain with relatively complex unsteady flow conditions were observed and investigated in detail.
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Leimeister, Mareike, Athanasios Kolios, and Maurizio Collu. "Development and Verification of an Aero-Hydro-Servo-Elastic Coupled Model of Dynamics for FOWT, Based on the MoWiT Library." Energies 13, no. 8 (April 16, 2020): 1974. http://dx.doi.org/10.3390/en13081974.
Full textAbstract:
The complexity of floating offshore wind turbine (FOWT) systems, with their coupled motions, aero-hydro-servo-elastic dynamics, as well as non-linear system behavior and components, makes modeling and simulation indispensable. To ensure the correct implementation of the multi-physics, the engineering models and codes have to be verified and, subsequently, validated for proving the realistic representation of the real system behavior. Within the IEA (International Energy Agency) Wind Task 23 Subtask 2 offshore code-to-code comparisons have been performed. Based on these studies, using the OC3 phase IV spar-buoy FOWT system, the Modelica for Wind Turbines (MoWiT) library, developed at Fraunhofer IWES, is verified. MoWiT is capable of fully-coupled aero-hydro-servo-elastic simulations of wind turbine systems, onshore, offshore bottom-fixed, or even offshore floating. The hierarchical programing and multibody approach in the object-oriented and equation-based modeling language Modelica have the advantage (over some other simulation tools) of component-based modeling and, hence, easily modifying the implemented system model. The code-to-code comparisons with the results from the OC3 studies show, apart from expected differences due to required assumptions in consequence of missing data and incomplete information, good agreement and, consequently, substantiate the capability of MoWiT for fully-coupled aero-hydro-servo-elastic simulations of FOWT systems.
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Ojo, Adebayo, Maurizio Collu, and Andrea Coraddu. "Parametrisation Scheme for Multidisciplinary Design Analysis and Optimisation of a Floating Offshore Wind Turbine Substructure – OC3 5MW Case Study." Journal of Physics: Conference Series 2265, no. 4 (May 1, 2022): 042009. http://dx.doi.org/10.1088/1742-6596/2265/4/042009.
Full textAbstract:
Abstract The development of novel energy technologies is considered imperative in the provision of solutions to meet an increasing global demand for clean energy. Floating Offshore Wind Turbine (FOWT) is one of the emerging technologies to exploit the vast wind resources available in deeper waters. To lower the levelized cost of energy (LCOE) or optimise the performance response associated with a FOWT system, a detailed understanding of the different disciplines (Aero-Hydro-Servo-Elastic) within the system and the relationship between the FOWT system and the dynamics of the marine environment is required. This requires an efficient Multidisciplinary Design, Analysis and Optimisation (MDAO) framework for FOWT systems to reduce the capital cost and increase dynamic performance. A key component of any MDAO framework is the shape parameterisation scheme, as it enables the modelling of a large array of platform designs with different geometric shapes using limited number of parameters. This work focuses on the B-Spline parameterisation modelling technique of OC3 spar-buoy and the use pattern search optimization algorithm to select the optimal design variants. The parametrisation technique is implemented in an analysis framework, where a B-spline library from Sesam GeniE is used to model each design representation, and a potential flow frequency domain analysis solver (HydroD/Wadam) is used for the hydrodynamic analysis. Validation of the selected designs within the design space is conducted with a benchmark NREL5MW spar-buoy hydrodynamic response results in literature with the hydrodynamic response of the frequency domain modelling approach using Sesam GeniE and HydroD/Wadam. This analysis process shows a high accuracy in response results between the OC3 spar-buoy in literature and the OC3 spar-buoy model design using B-Spline parametrization technique. Key performance metrics like the cost of materials and root mean square (RMS) of the nacelle acceleration also show improvement with the design variants compared to estimation from OC3 design in literature.