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1
Nielsen, Kim, et Jonas Thomsen. « KNSwing—On the Mooring Loads of a Ship-Like Wave Energy Converter ». Journal of Marine Science and Engineering 7, no 2 (1 février 2019) : 29. http://dx.doi.org/10.3390/jmse7020029.
Texte intégralRésumé :
The critical function of keeping a floating Wave Energy Converter in position is done by a mooring system. Several WECs have been lost due to failed moorings, indicating that extreme loads, reliability and durability are very important aspects. An understanding of the interaction between the WEC’s motion in large waves and the maximum mooring loads can be gained by investigating the system at model scale supported by numerical models. This paper describes the testing of a novel attenuator WEC design called KNSwing. It is shaped like a ship facing the waves with its bow, which results in low mooring loads and small motions in most wave conditions when the structure is longer than the waves. The concept is tested using an experimental model at scale 1:80 in regular and irregular waves, moored using rubber bands to simulate synthetic moorings. The experimental results are compared to numerical simulations done using the OrcaFlex software. The experimental results show that the WEC and the mooring system survives well, even under extreme and breaking waves. The numerical model coefficient concerning the nonlinear drag term for the surge motion is validated using decay tests. The numerical results compare well to the experiments and, thereby, the numerical model can be further used to optimize the mooring system.
2
Xue, Gang, Jian Qin, Zhenquan Zhang, Shuting Huang et Yanjun Liu. « Experimental Investigation of Mooring Performance and Energy-Harvesting Performance of Eccentric Rotor Wave Energy Converter ». Journal of Marine Science and Engineering 10, no 11 (18 novembre 2022) : 1774. http://dx.doi.org/10.3390/jmse10111774.
Texte intégralRésumé :
To obtain the optimal mooring mode and the best-matching wave condition of an eccentric rotor wave energy converter (ERWEC), a physical model of the ERWEC was developed. Ten mooring modes and eight wave conditions were set up. Several experiments were carried out to analyze the influence of mooring modes and wave conditions on the mooring and energy-harvesting performances of the ERWEC. The results showed that the mooring and energy-harvesting performances changed significantly for the same mooring mode under various regular wave conditions, but the opposite situation was found under irregular wave conditions. The wave-facing direction of the buoy was a critical factor affecting the mooring and energy-harvesting performances, while the number of anchor lines had little effect on them. In addition, a method to evaluate the motion response of the buoy based on the number of effective excitations and a method to evaluate the comprehensive performance based on the cloud chart are proposed. The mooring mode and wave condition combination that obtained the optimal mooring and energy-harvesting performances for the ERWEC was determined. This paper provides a novel perspective on how to balance the efficiency and reliability of wave energy converters.
3
Cross, Patrick, et Krishnakumar Rajagopalan. « Wave Energy Converter Deployments at the Navy's Wave Energy Test Site : 2015‐2019 ». Marine Technology Society Journal 54, no 6 (1 novembre 2020) : 91–96. http://dx.doi.org/10.4031/mtsj.54.6.8.
Texte intégralRésumé :
AbstractA synopsis of wave energy converter (WEC) deployments at the U.S. Navy's Wave Energy Test Site (WETS), from the mid-2015 commissioning of the full three-berth site through 2019, is provided. This includes two deployments each of the Northwest Energy Innovations (NWEI) Azura device and the Fred. Olsen Ltd. BOLT Lifesaver, each with important modifications between deployments. The Azura was modified with a larger float and a heave plate, aimed at enhancing power performance, while the Lifesaver's second deployment addressed mooring challenges encountered in the first. Additionally, unique integration and deployment of a sophisticated environmental sensing system developed by the University of Washington, in which required power was drawn from the WEC itself, was achieved during this second Lifesaver deployment. A brief background of the site is included, as is a synopsis of two major efforts not directly related to WEC deployments—the development of a site-dedicated support vessel and work to redesign and make repairs to the WETS deep berth mooring systems, including the addition of a “no-WEC hawser” system to keep the moorings in tension between WEC deployments. Finally, a look ahead to WEC deployments planned in 2021‐2023 is provided.
4
Nwaoha, Thaddeus C., et Nsisong E. Udosoh. « Facilitating optimal operations of wave energy converter using a preeminent mooring line : an entropy weight-VIKOR method ». Journal of Mechanical and Energy Engineering 6, no 1 (1 juillet 2022) : 77–84. http://dx.doi.org/10.30464/jmee.2022.6.1.77.
Texte intégralRésumé :
This study employed viable methods for the selection of a preeminent mooring line amongst other alternatives for the mooring of a floating wave energy converter (WEC) in shallow water. Conventional mooring lines for mooring WEC are identified for optimal selection exercise. A combination of Entropy Weight and Visekriterijumska Optimizacijia I Kompromisno Resenje (VIKOR) methods is utilized in the aforementioned exercise. The two methods are effectively used in assessment of the attributes and performance of the various mooring lines in practical application. The result obtained, demonstrated that steel wire rope is the best mooring line suitable for a WEC system operations. It is good references to the marine and offshore engineering industries in decision making for optimal mooring line suitable for the mooring of a WEC system in shallow waters.
5
Qiao, Dongsheng, Rizwan Haider, Jun Yan, Dezhi Ning et Binbin Li. « Review of Wave Energy Converter and Design of Mooring System ». Sustainability 12, no 19 (7 octobre 2020) : 8251. http://dx.doi.org/10.3390/su12198251.
Texte intégralRésumé :
In recent decades, the emphasis on renewable resources has grown considerably, leading to significant advances in the sector of wave energy. Nevertheless, the market cannot still be considered as commercialized, as there are still other obstacles in the mooring system for wave energy converters (WECs). The mooring system must be designed to not negatively impact the WEC’s efficiency and reduce the mooring loads. Firstly, the overview of the types of wave energy converters (WECs) are classified through operational principle, absorbing wave direction, location, and power take-off, respectively, and the power production analysis and design challenges of WECs are summarized. Then, the mooring materials, configurations, requirements, and the modeling approaches for WECs are introduced. Finally, the design of mooring systems, including the design considerations and standards, analysis models, software, current research focus, and challenges are discussed.
6
Meng, Zhongliang, Yanjun Liu, Jian Qin et Shumin Sun. « Mooring Angle Study of a Horizontal Rotor Wave Energy Converter ». Energies 14, no 2 (9 janvier 2021) : 344. http://dx.doi.org/10.3390/en14020344.
Texte intégralRésumé :
The horizontal rotor wave energy converter is a newly designed wave energy converter. While the mooring system plays a vital role in keeping the device floating stably, the selection of the mooring angle has immediate effects on the device’s floating stability and energy generation efficiency. Given the properties of wave energy along the coast in Shandong Province, this study combines wave statistics gathered from field measurements of a certain area in the Bohai Sea with hydrological data obtained in a field test in the same sea area and adopts Stokes’ fifth-order wave theory to theoretically design and simulate the mooring system for the new type of power generating device. With the help of AQWA software, data on the dynamics of the device at various angles are obtained to construct models and carry out regular wave experiments according to the most appropriate mooring angles to show the validity of the selected mooring angles. The consistency of the results between the experiment and simulation confirms that under the same working conditions of regular waves, as the mooring angle increases, the roll angle decreases first and then increases, the pitch angle barely varies, and the yaw angle decreases first and then increases. The adoption of this simulation method and the gathered experimental data help to provide theoretical and practical bases for choosing the mooring method for the engineering prototype and obtaining a reliable supply of power.
7
Meng, Zhongliang, Yanjun Liu, Jian Qin et Shumin Sun. « Mooring Angle Study of a Horizontal Rotor Wave Energy Converter ». Energies 14, no 2 (9 janvier 2021) : 344. http://dx.doi.org/10.3390/en14020344.
Texte intégralRésumé :
The horizontal rotor wave energy converter is a newly designed wave energy converter. While the mooring system plays a vital role in keeping the device floating stably, the selection of the mooring angle has immediate effects on the device’s floating stability and energy generation efficiency. Given the properties of wave energy along the coast in Shandong Province, this study combines wave statistics gathered from field measurements of a certain area in the Bohai Sea with hydrological data obtained in a field test in the same sea area and adopts Stokes’ fifth-order wave theory to theoretically design and simulate the mooring system for the new type of power generating device. With the help of AQWA software, data on the dynamics of the device at various angles are obtained to construct models and carry out regular wave experiments according to the most appropriate mooring angles to show the validity of the selected mooring angles. The consistency of the results between the experiment and simulation confirms that under the same working conditions of regular waves, as the mooring angle increases, the roll angle decreases first and then increases, the pitch angle barely varies, and the yaw angle decreases first and then increases. The adoption of this simulation method and the gathered experimental data help to provide theoretical and practical bases for choosing the mooring method for the engineering prototype and obtaining a reliable supply of power.
8
Qiao, Dongsheng, et Jinping Ou. « Mooring Line Damping Estimation for a Floating Wind Turbine ». Scientific World Journal 2014 (2014) : 1–10. http://dx.doi.org/10.1155/2014/840283.
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The dynamic responses of mooring line serve important functions in the station keeping of a floating wind turbine (FWT). Mooring line damping significantly influences the global motions of a FWT. This study investigates the estimation of mooring line damping on the basis of the National Renewable Energy Laboratory 5 MW offshore wind turbine model that is mounted on the ITI Energy barge. A numerical estimation method is derived from the energy absorption of a mooring line resulting from FWT motion. The method is validated by performing a 1/80 scale model test. Different parameter changes are analyzed for mooring line damping induced by horizontal and vertical motions. These parameters include excitation amplitude, excitation period, and drag coefficient. Results suggest that mooring line damping must be carefully considered in the FWT design.
9
Cai, Yuanzhen, Milad Bazli, Asanka P. Basnayake, Martin Veidt et Michael T. Heitzmann. « Composite Springs for Mooring Tensioners : A Systematic Review of Material Selection, Fatigue Performance, Manufacturing, and Applications ». Journal of Marine Science and Engineering 10, no 9 (12 septembre 2022) : 1286. http://dx.doi.org/10.3390/jmse10091286.
Texte intégralRésumé :
Ocean energy is an underutilized renewable energy source compared with hydropower and wind power. Therefore, the development of economical and efficient wave energy converters (WECs) is important and crucial for offshore power generation. The mooring tensioner is a critical device that can be used in point-absorber-type WECs, semisubmersible floats for oil and gas drilling, and floating wind turbines. A mooring tensioner is a system used to create, reduce, or maintain tension within the mooring lines by applying a force to the mooring line. Composite springs as mooring tensioners have several advantages compared to metal springs, such as corrosion resistance, high specific strain energy, appropriate fatigue performance, and the ability to flexibly adjust the spring constant without changing the overall dimensions. This paper reviews in detail the fatigue performance, seawater durability, and manufacturing methods of different composite materials as well as the current and potential applications of composites springs. In addition, recommendations for future research and opportunities for composite mooring tensioners are presented.
10
Liu, Shi, Yi Yang, Chengyuan Wang, Yuangang Tu et Zhenqing Liu. « Proposal of a Novel Mooring System Using Three-Bifurcated Mooring Lines for Spar-Type Off-Shore Wind Turbines ». Energies 14, no 24 (9 décembre 2021) : 8303. http://dx.doi.org/10.3390/en14248303.
Texte intégralRésumé :
Floating wind turbine vibration controlling becomes more and more important with the increase in wind turbine size. Thus, a novel three-bifurcated mooring system is proposed for Spar-type floating wind turbines. Compared with the original mooring system using three mooring lines, three-bifurcated sub-mooring-lines are added into the novel mooring system. Specifically, each three-bifurcated sub-mooring-line is first connected to a Spar-type platform using three fairleads, then it is connected to the anchor using the main mooring line. Six fairleads are involved in the proposed mooring system, theoretically resulting in larger overturning and torsional stiffness. For further improvement, a clump mass is attached onto the main mooring lines of the proposed mooring system. The wind turbine surge, pitch, and yaw movements under regular and irregular waves are calculated to quantitatively examine the mooring system performances. A recommended configuration for the proposed mooring system is presented: the three-bifurcated sub-mooring-line and main mooring line lengths should be (0.0166, 0.0111, 0.0166) and 0.9723 times the total mooring line length in the traditional mooring system. The proposed mooring system can at most reduce the wind turbine surge movement 37.15% and 54.5% when under regular and irregular waves, respectively, and can at most reduce the yaw movement 30.1% and 40% when under regular and irregular waves, respectively.
11
Martinelli, Luca, Piero Ruol et Giampaolo Cortellazzo. « ON MOORING DESIGN OF WAVE ENERGY CONVERTERS : THE SEABREATH APPLICATION ». Coastal Engineering Proceedings 1, no 33 (15 octobre 2012) : 3. http://dx.doi.org/10.9753/icce.v33.structures.3.
Texte intégralRésumé :
The design of a mooring system of a Wave Energy Converter is a challenging process that points out several unsolved technical problems, mostly related to the highly non-linear hydrodynamic phenomena occurring when high waves (e.g. 8 m high with 200 m wavelength) propagate in relatively shallow waters (e.g. 20 m). The aim of this note is to point out the relevance of the non-linear response of a WEC anchored in relatively shallow waters (shallow in the “non-linear” sense) in terms of loads applied to the mooring lines. Further, the effects of this cyclic load on the anchors is investigated. Note that to some extent it is like checking the importance of geotechnical and coastal engineers in the design process of the WEC structure and its mooring system (typically carried out by naval architects). The whole mooring design process is first outlined and then it is schematically applied to a specific case, namely a promising Italian device named SeaBreath (www.seabreath.it), in view of a possible deployment in the Adriatic Sea. The main concern of mooring designers is related to resonance effects induced by the second order drift. Therefore specific tests have been carried out in the 36 m long x 1.0 m wide x 1.3 m high wave flume of Padova University. Tests focused on the forces on the mooring lines induced by the sum of two regular waves of similar frequency. The mooring design is still far from complete: the physical model proved the relevance of the aforementioned effects but a numerical investigation (not yet performed) is required to draw final conclusions.
12
Silverthorne, Katherine E., et John M. Toole. « Seasonal Kinetic Energy Variability of Near-Inertial Motions ». Journal of Physical Oceanography 39, no 4 (1 avril 2009) : 1035–49. http://dx.doi.org/10.1175/2008jpo3920.1.
Texte intégralRésumé :
Abstract Seasonal variability of near-inertial horizontal kinetic energy is examined using observations from a series of McLane Moored Profiler moorings located at 39°N, 69°W in the western North Atlantic Ocean in combination with a one-dimensional, depth-integrated kinetic energy model. The time-mean kinetic energy and shear vertical wavenumber spectra of the high-frequency motions at the mooring site are in reasonable agreement with the Garrett–Munk internal wave description. Time series of depth-dependent and depth-integrated near-inertial kinetic energy are calculated from available mooring data after filtering to isolate near-inertial-frequency motions. These data document a pronounced seasonal cycle featuring a wintertime maximum in the depth-integrated near-inertial kinetic energy deriving chiefly from the variability in the upper 500 m of the water column. The seasonal signal in the near-inertial kinetic energy is most prominent for motions with vertical wavelengths greater than 100 m but observable wintertime enhancement is seen down to wavelengths of the order of 10 m. Rotary vertical wavenumber spectra exhibit a dominance of clockwise-with-depth energy, indicative of downward energy propagation and implying a surface energy source. A simple depth-integrated near-inertial kinetic energy model consisting of a wind forcing term and a dissipation term captures the order of magnitude of the observed near-inertial kinetic energy as well as its seasonal cycle.
13
Martinelli, Luca, et Barbara Zanuttigh. « Effects of Mooring Compliancy on the Mooring Forces, Power Production, and Dynamics of a Floating Wave Activated Body Energy Converter ». Energies 11, no 12 (19 décembre 2018) : 3535. http://dx.doi.org/10.3390/en11123535.
Texte intégralRésumé :
The paper aims at investigating the interactions between a floating wave energy device (WEC) and its mooring system under a variety of wave conditions (regular and irregular, perpendicular and oblique, ordinary and extreme). The analyzed WEC is the DEXA, a wave activated body point absorber, of the type that performs better when aligned to the incident wave direction. Two typologies of mooring systems were studied: for limited depths, the spread system, with a disposition of the lines that do not constrain the yaw movements; for large depths, the catenary anchor leg mooring (CALM) system. The spread system was experimentally investigated, including a realistic power take-off system, to capture non-linear behaviors and assess device motions, power production, and forces on mooring lines. The CALM system was numerically simulated, as mooring modelling is more reliable in deep waters and allows testing of a number of different configurations, by changing the number of the mooring lines and the mooring layout. The experiments showed that a reduction of the mooring compliancy increases the power production. The numerical simulations showed that a redundancy on the number of chains allows a better distribution of the loads, with advantages on reliability and costs.
14
Bach-Gansmo, Magnus Thorsen, Stian Kielland Garvik, Jonas Bjerg Thomsen et Morten Thøtt Andersen. « Parametric Study of a Taut Compliant Mooring System for a FOWT Compared to a Catenary Mooring ». Journal of Marine Science and Engineering 8, no 6 (12 juin 2020) : 431. http://dx.doi.org/10.3390/jmse8060431.
Texte intégralRésumé :
The catenary mooring system is a well recognized station keeping method. However, there could be economical and environmental benefits of reducing the footprint. In the last decades, more focus has been given to synthetic mooring lines and different mooring layouts to optimize the levelized cost of energy (LCOE) for offshore renevable energy converters such as wave energy converters. Therefore, this work presents a parametric study of two important parameters, namely the mooring line angle and line pretension, for a taut mooring configuration focusing on the dynamic response when applied to the TetraSpar floating foundation compared to a catenary mooring system. The work is based on experimental results conducted in the wave basin at Aalborg University (AAU) and compared to analytical stiffness calculations. In addition, a numerical model was tuned based on the main dynamics to achieve the tension response. The results showed satisfying dynamic behavior where the angle and pretension mainly influenced the surge and yaw natural periods. The motion response showed similar behavior between the chosen parameters, and larger pitch amplitudes were found compared to the catenary system.
15
Pols, Alana, Eric Gubesch, Nagi Abdussamie, Irene Penesis et Christopher Chin. « Mooring Analysis of a Floating OWC Wave Energy Converter ». Journal of Marine Science and Engineering 9, no 2 (20 février 2021) : 228. http://dx.doi.org/10.3390/jmse9020228.
Texte intégralRésumé :
This investigation focuses on the modelling of a floating oscillating water column (FOWC) wave energy converter with a numerical code (ANSYS AQWA) based on potential flow theory. Free-floating motions predicted by the numerical model were validated against experimental data extrapolated from a 1:36 scale model device in regular and irregular sea states. Upon validation, an assessment of the device’s motions when dynamically coupled with a four-line catenary mooring arrangement was conducted at different incident wave angles and sea states ranging from operational to survivable conditions, including the simulation of the failure of a single mooring line. The lack of viscosity in the numerical modelling led to overpredicted motions in the vicinity of the resonant frequencies; however, the addition of an external linear damping coefficient was shown to be an acceptable method of mitigating these discrepancies. The incident wave angle was found to have a limited influence on the magnitudes of heave, pitch, and surge motions. Furthermore, the obtained results indicated that the mooring restoring force is controlled by the forward mooring lines under the tested conditions.
16
Paduano, Bruno, Giuseppe Giorgi, Rui P. F. Gomes, Edoardo Pasta, João C. C. Henriques, Luís M. C. Gato et Giuliana Mattiazzo. « Experimental Validation and Comparison of Numerical Models for the Mooring System of a Floating Wave Energy Converter ». Journal of Marine Science and Engineering 8, no 8 (27 juillet 2020) : 565. http://dx.doi.org/10.3390/jmse8080565.
Texte intégralRésumé :
The mooring system of floating wave energy converters (WECs) has a crucial impact on power generation efficiency, cost of delivered energy, proper operation, reliability and survivability. An effective design, addressing such competing objectives, requires appropriate mathematical models to predict mooring loads and dynamic response. However, conversely to traditional offshore engineering applications, experience in modelling mooring systems for WECs is limited, due to their unique requirement of maximising the motion while minimising loads and costs. Even though modelling approaches and software are available for this application, guidelines and critical comparison are still scarce. This paper proposes a discussion and validation of three mooring-line models: one quasi-static approach (developed in-house) and two dynamic lumped-mass approaches (the open source MoorDyn and the commercial OrcaFlex). The case study is a 1:32-scale prototype of a floating oscillating water column WEC tested in a wave tank, with three mooring lines, each one comprising of a riser and a clump weight. Validation, performed by imposing fairlead displacements and comparing resulting tensions, shows good agreement. The small scale may induce numerical instabilities and uncertainties in the parameter estimation. Finally, likely due to internal resonance of this particular mooring system, high-frequency content in the mooring tension is found, albeit absent in the kinematics of the floater.
17
Li, Chun Bao, Mingsheng Chen et Joonmo Choung. « The Quasi-Static Response of Moored Floating Structures Based on Minimization of Mechanical Energy ». Journal of Marine Science and Engineering 9, no 9 (3 septembre 2021) : 960. http://dx.doi.org/10.3390/jmse9090960.
Texte intégralRésumé :
It is essential to design a reasonable mooring line length that ensures quasi-static responses of moored floating structures are within an acceptable level, and that reduces the cost of mooring lines in the overall project. Quasi-static responses include the equilibrium position and the line tension of a moored floating structure (also called the mean value in a dynamic response), etc. The quasi-static responses derived by the classic catenary equation cannot present mooring–seabed interaction and hydrodynamic effects on a mooring line. While a commercial program can predict reasonable quasi-static responses, costly modeling is required. This motivated us to propose a new method for predicting quasi-static responses that minimizes the mechanical energy of the whole system based on basic geometric parameters, and that is easy to implement. In this study, the mechanical energy of moored floating structures is assumed to be the sum of gravitational–buoyancy potential energy, kinetic energy induced by drag forces, and spring potential energy derived by line tension. We introduce fundamental theoretical background for the development of the proposed method. We investigate the effect of quasi-static actions on mooring response, comparing the proposed method’s results with those from the catenary equation and ABAQUS software. The study reveals the shortcomings of the catenary equation in offshore applications. We also compare quasi-static responses derived by the AQWA numerical package with the results calculated from the proposed method for an 8 MW WindFloat 2 type of platform. Good agreement was drawn between the proposed method and AQWA. The proposed method proves more timesaving than AQWA in terms of modeling of mooring lines and floaters, and more accurate than the catenary equation, and can be used effectively in the early design phase of dimension mooring lengths for moored floating structures.
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Formosa, W., et T. Sant. « Modelling the loads and motions of a floating offshore wind turbine with asymmetric moorings ». Journal of Physics : Conference Series 2362, no 1 (1 novembre 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.
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Qiao, Dong Sheng, et Jin Ping Ou. « Parameter Calculation of Viscous Damper Applied in the Truncated Model Test Design of a Deepwater Semi-Submersible Platform ». Advanced Materials Research 168-170 (décembre 2010) : 1480–85. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.1480.
Texte intégralRésumé :
In the equivalent water depth truncated model test design of a deepwater semi-submersible platform, the viscous damper is designed to simulate the contribution of mooring damping to total damping of floating platform. The dissipated energy by a mooring line from the floating platform as a result of its oscillation is applied to calculate the mooring-induced damping. The mooring line and seabed interaction is based on the hypothesis of rigid seabed. The fluid drag force and inertia force on the mooring line are calculated according to the Morrison formula. The non-liner dynamic analysis of mooring line is executed in the time domain based on the finite element method. The mooring induced damping is obtained from the results. The value difference of mooring induced damping between the truncated and full-depth mooring line is linearized to provide parameter for the design of viscous damper.
20
Depalo, Francesco, Shan Wang, Sheng Xu et C. Guedes Soares. « Design and Analysis of a Mooring System for a Wave Energy Converter ». Journal of Marine Science and Engineering 9, no 7 (19 juillet 2021) : 782. http://dx.doi.org/10.3390/jmse9070782.
Texte intégralRésumé :
The objective of this work is to develop an efficient method to carry out the preliminary design of the mooring system for a wave energy converter. A practical mooring design procedure is applied to a specific case of study, and it can be replicated for other cases. Firstly, the static analysis is performed for a configuration with three mooring cables with different pre-tensions on fairlead, diameters of the cables, and materials. Based on these configurations from the static analysis, a quasi-static analysis is carried out in the frequency domain and a preliminary design is conducted according to DNV rules. Then, a 3-h dynamic analysis in the time domain is performed on several selected configurations, considering the same environmental conditions in the quasi-static analysis using the finite element method. Extreme dynamic responses of the system, such as extreme surge motion and mooring tensions, are estimated by the global maximum method, which is performed by fitting 20 individual maximum observations by Gumbel distribution. The quasi-static method is validated by comparing the results of extreme tension and displacement with the coupled time domain analysis. In addition, the influence of pre-tensions and cable diameters on the static and dynamic responses of the mooring system are discussed.
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Sirigu, Sergej Antonello, Mauro Bonfanti, Ermina Begovic, Carlo Bertorello, Panagiotis Dafnakis, Giuseppe Giorgi, Giovanni Bracco et Giuliana Mattiazzo. « Experimental Investigation of the Mooring System of a Wave Energy Converter in Operating and Extreme Wave Conditions ». Journal of Marine Science and Engineering 8, no 3 (7 mars 2020) : 180. http://dx.doi.org/10.3390/jmse8030180.
Texte intégralRésumé :
A proper design of the mooring systems for Wave Energy Converters (WECs) requires an accurate investigation of both operating and extreme wave conditions. A careful analysis of these systems is required to design a mooring configuration that ensures station keeping, reliability, maintainability, and low costs, without affecting the WEC dynamics. In this context, an experimental campaign on a 1:20 scaled prototype of the ISWEC (Inertial Sea Wave Energy Converter), focusing on the influence of the mooring layout on loads in extreme wave conditions, is presented and discussed. Two mooring configurations composed of multiple slack catenaries with sub-surface buoys, with or without clump-weights, have been designed and investigated experimentally. Tests in regular, irregular, and extreme waves for a moored model of the ISWEC device have been performed at the University of Naples Federico II. The aim is to identify a mooring solution that could guarantee both correct operation of the device and load carrying in extreme sea conditions. Pitch motion and loads in the rotational joint have been considered as indicators of the device hydrodynamic behavior and mooring configuration impact on the WEC.
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Johanning, L., G. H. Smith et J. Wolfram. « Mooring design approach for wave energy converters ». Proceedings of the Institution of Mechanical Engineers, Part M : Journal of Engineering for the Maritime Environment 220, no 4 (décembre 2006) : 159–74. http://dx.doi.org/10.1243/14750902jeme54.
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Giannini, Gianmaria, Paulo Rosa-Santos, Victor Ramos et Francisco Taveira-Pinto. « On the Development of an Offshore Version of the CECO Wave Energy Converter ». Energies 13, no 5 (26 février 2020) : 1036. http://dx.doi.org/10.3390/en13051036.
Texte intégralRésumé :
Offshore locations present significant amounts of wave energy and free sea space, which could facilitate the deployment of larger numbers of wave energy converters (WECs) in comparison with nearshore regions. The present study aims to find a suitable design for an offshore floating version of CECO, a sloped motion WEC. For this purpose, a new design methodology is proposed in this paper for identifying and assessing possible floating configurations of CECO, which consists of four distinct set-ups obtained by varying the type of main supporting structure and the mooring system. Two options are based on spar designs and the other two on tension leg platform (TLP) designs. Based on outcomes of time-domain numerical calculations, the aforementioned configurations were assessed in terms of annual wave energy conversion and magnitude of mooring loads. Results indicate that a TLP configuration with an innovative mooring solution could increase the annual energy production by 40% with respect to the fixed version of CECO. Besides, the mooring system is found to be a key component, influencing the overall system performance.
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Yu, Long Fei, et Liang Sheng Zhu. « Hydrodynamic Response of Wave Energy Converters under Complex Sea State ». Applied Mechanics and Materials 501-504 (janvier 2014) : 1919–26. http://dx.doi.org/10.4028/www.scientific.net/amm.501-504.1919.
Texte intégralRésumé :
In real sea state, Ocean energy devices to work hard to stabilize, or even destroyed. Based on Airy wave theory, Movement and force of heaving cylindrical wave-energy converter (WEC) was analyzed under the complex marine state. Then setting the South China coast as the environmental background, and simulating and computing the motion response of the buoy and the mooring system under various sea conditions. The computational data show that complex mechanical response was happened and the mooring system (SM) has excellent mooring performance. The research results have practical significance for heaving cylindrical WEC survival design under real sea conditions.
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Ahmed, Montasir Osman, Anurag Yenduri et V. John Kurian. « Behaviour of Mooring Systems for Different Line Pretensions ». Applied Mechanics and Materials 567 (juin 2014) : 204–9. http://dx.doi.org/10.4028/www.scientific.net/amm.567.204.
Texte intégralRésumé :
Mooring lines are the most commonly used station-keeping systems for floating platforms as they are easy to install and relocate. The mooring lines are usually pre-tensioned so as to use their energy absorption to reduce the platform motions and thereby, to lower the forces in the lines. To decide on the preliminary design of the platforms, it is necessary to investigate the restoring behaviour of the mooring systems for various parameters. In this study, two different mooring configurations with and without mooring line in wave heading direction are considered for determining its behaviour for various pretensions in the lines. A MATLAB code named QSAML has been developed using quasi-static approach to compute the restoring forces of the mooring system. The code is validated with experimental tests and used in this study. It has been observed that with increase in pretension of the mooring line, restoring performance of the mooring system can be improved. The maximum permissible excursions by mooring system in the wave heading direction are found to be more for relatively lower pretension values.
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Syarif Arief, Irfan, I. Ketut Aria Pria Utama, Ridho Hantoro, Juniarko Prananda et Alfa Muhammad Megawan. « Computational Fluid Dynamics (CFD) Simulation for Designing Mooring Bitts Position at the Barge for Wave Energy Conversion (WEC) ». E3S Web of Conferences 190 (2020) : 00017. http://dx.doi.org/10.1051/e3sconf/202019000017.
Texte intégralRésumé :
Potential wave energy in Indonesia between 5 kW m–1 to 20 kW m–1 depending on-site location coastline. This research in ocean energy of Wave Energy Conversion (WEC) is wave activated body using the floating or motion hull due to kinetic and momentum energy from an ocean wave. The pendulum movement cause by a floating hull to drive the electric generator. The shape of the hull, displacement, and position point of the mooring line greatly influences the movement of the hull. This paper discusses how to computational fluid dynamics (CFD) simulation can solve and determine the best mooring line position in the hull. Moreover, the shape of the hull at under waterline or drought has slope angle 45°, length overall 3 m, breadth 1.5 m, depth 2 m, and draft 0.65 m. One of the boundary conditions in the domain CFD, the direction of a wave from inlet boundary to starboard or port side using regular wave. The position both of mooring bitts are at forwarding perpendicular and after perpendicular. Three-position of mooring bitts that have simulated CFD: under the waterline, (ii) at the waterline, and (iii) up waterline. The result of simulation that the best position of mooring bitts is at the waterline.
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Touzon, Imanol, Vincenzo Nava, Borja de Miguel et Victor Petuya. « A Comparison of Numerical Approaches for the Design of Mooring Systems for Wave Energy Converters ». Journal of Marine Science and Engineering 8, no 7 (16 juillet 2020) : 523. http://dx.doi.org/10.3390/jmse8070523.
Texte intégralRésumé :
This paper analyses the numerical outcome of applying three different well-known mooring design approaches to a floating wave energy converter, moored by means of four catenary lines. The approaches include: a linearized frequency domain based on a quasistatic model of the mooring lines, a time domain approach coupled with an analytic catenary model of the mooring system, and a fully coupled non-linear time domain approach, considering lines’ drag and inertia forces. Simulations have been carried out based on a set of realistic combinations of lines pretension and linear mass, subject to extreme environmental conditions. Obtained results provide realistic cost and performance indicators, presenting a comparison in terms of total mooring mass and required footprint, as well as the design line tension and structure offset. It has been found that lines’ viscous forces influence significantly the performance of the structure with high pretensions, i.e., >1.2, while there is acceptable agreement between the modelling approaches with lower pretensions. Line tensions are significantly influenced by drag and inertia forces because of the occurrence of snap loads due to the heaving of the floater. However, the frequency domain approach provides an insight towards the optimal design of the mooring system for preliminary designs.
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Boo, Sung Youn, et Steffen Allan Shelley. « Design and Analysis of a Mooring Buoy for a Floating Arrayed WEC Platform ». Processes 9, no 8 (10 août 2021) : 1390. http://dx.doi.org/10.3390/pr9081390.
Texte intégralRésumé :
This paper presents the design and analysis of a mooring buoy and its mooring systems to moor a floating platform mounting an arrayed Wave Energy Converters (WECs). The mooring buoy allows the WEC platform to weathervane around the mooring buoy freely by the prevailing environment directions, which enables consistent power generation. The WEC platform is connected to the buoy with synthetic hawsers, while station-keeping of the buoy is maintained with catenary mooring lines of chains tied to the buoy keel. The buoy also accommodates a power cable to transfer the electricity from the WEC platform to the shore. The WEC platform is designed to produce a total of 1.0 MW with multiple WECs installed in an array. Fully coupled time-domain analyses are conducted under the site sea states, including extreme 50 y and survival 100 y conditions. The buoy motions, mooring tensions and other design parameters are evaluated. Strength and fatigue designs of the mooring systems are validated with requirements according to industry standards. Global and local structural designs of the mooring buoy are carried out and confirm the design compliances.
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Faizal, Mohammed, M. Rafiuddin Ahmed et Young-Ho Lee. « A Design Outline for Floating Point Absorber Wave Energy Converters ». Advances in Mechanical Engineering 6 (1 janvier 2014) : 846097. http://dx.doi.org/10.1155/2014/846097.
Texte intégralRésumé :
An overview of the most important development stages of floating point absorber wave energy converters is presented. At a given location, the wave energy resource has to be first assessed for varying seasons. The mechanisms used to convert wave energy to usable energy vary for different wave energy conversion systems. The power output of the generator will have variations due to varying incident waves. The wave structure-interaction leads to modifications in the incident waves; thus, the power output is also affected. The device has to be stable enough to prevent itself from capsizing. The point absorber will give optimum performance when the incident wave frequencies correspond to the natural frequency of the device. The methods for calculating natural frequencies for pitching and heaving systems are presented. Mooring systems maintain the point absorber at the desired location. Various mooring configurations as well as the most commonly used materials for mooring lines are discussed. An overview of scaled modelling is also presented.
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Moura Paredes, Guilherme, Claes Eskilsson et Allan P. Engsig-Karup. « Uncertainty Quantification in Mooring Cable Dynamics Using Polynomial Chaos Expansions ». Journal of Marine Science and Engineering 8, no 3 (2 mars 2020) : 162. http://dx.doi.org/10.3390/jmse8030162.
Texte intégralRésumé :
Mooring systems exhibit high failure rates. This is especially problematic for offshore renewable energy systems, like wave and floating wind, where the mooring system can be an active component and the redundancy in the design must be kept low. Here we investigate how uncertainty in input parameters propagates through the mooring system and affects the design and dynamic response of mooring and floaters. The method used is a nonintrusive surrogate based uncertainty quantification (UQ) approach based on generalized Polynomial Chaos (gPC). We investigate the importance of the added mass, tangential drag, and normal drag coefficient of a catenary mooring cable on the peak tension in the cable. It is found that the normal drag coefficient has the greatest influence. However, the uncertainty in the coefficients plays a minor role for snap loads. Using the same methodology we analyze how deviations in anchor placement impact the dynamics of a floating axi-symmetric point-absorber. It is shown that heave and pitch are largely unaffected but surge and cable tension can be significantly altered. Our results are important towards streamlining the analysis and design of floating structures. Improving the analysis to take into account uncertainties is especially relevant for offshore renewable energy systems where the mooring system is a considerable portion of the investment.
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Meng, Zhongliang, Yun Chen, Yanjun Liu et Yi Ding. « Mooring Stability Study for Novel Wave Energy Converter Based on Regular Wave ». Journal of Marine Science and Engineering 9, no 10 (7 octobre 2021) : 1095. http://dx.doi.org/10.3390/jmse9101095.
Texte intégralRésumé :
The mooring system not only plays a vital role in keeping wave energy generators floating stably, but also affects the success of engineering design. Combining wave force theory and the hydrological data obtained from the field measurements of a certain sea area in the Bohai Sea, the Stokes second-order wave theory was adopted to design the mooring system of a new type of power-generating device. At the same time, the study uses the Aqwa software to gather the dynamic data of a power-generating device in a real test, and then makes models and carries out regular wave tests so as to verify the viability of the mooring system and the stability of the whole power-generating device. All of this work will provide a theoretical basis for the manufacture of an engineering prototype and its reliable supply of power.
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Liu, Ya-qiong, Nian-xin Ren et Jin-ping Ou. « Investigation on Effects of Mooring Line Fractures and Connector Failures for A Hybrid Modular Floating Structure System ». China Ocean Engineering 36, no 6 (décembre 2022) : 880–93. http://dx.doi.org/10.1007/s13344-022-0079-7.
Texte intégralRésumé :
AbstractThe present work reports a Hybrid Modular Floating Structure (HMFS) system with typical malfunction conditions. The effects of both fractured mooring lines and failed connectors on main hydrodynamic responses (mooring line tensions, module motions, connector loads and wave power production) of the HMFS system under typical sea conditions are comparatively investigated. The results indicate that the mooring tension distribution, certain module motions (surge, sway and yaw) and connector loads (Mz) are significantly influenced by mooring line fractures. The adjacent mooring line of the fractured line on the upstream side suffers the largest tension among the remaining mooring lines, and the case with two fractured mooring lines in the same group on the upstream side is the most dangerous among all cases of two-line failures in view of mooring line tensions, module motions and connector loads. Therefore, one emergency strategy with appropriate relaxation of a proper mooring line has been proposed and proved effective to reduce the risk of more progressive mooring line fractures. In addition, connector failures substantially affect certain module motions (heave and pitch), certain connector loads (Fz and My) and wave power production. The present work can be helpful and instructive for studies on malfunction conditions of modular floating structure (MFS) systems.
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Gözcü, Ozan, Stavros Kontos et Henrik Bredmose. « Dynamics of two floating wind turbines with shared anchor and mooring lines ». Journal of Physics : Conference Series 2265, no 4 (1 mai 2022) : 042026. http://dx.doi.org/10.1088/1742-6596/2265/4/042026.
Texte intégralRésumé :
Abstract Floating wind farms present the opportunity to harvest wind resources located in deep water sites. Shared mooring designs can contribute in making floating wind energy more cost-competitive, and it is important to understand the new system dynamics that arise. We are presenting here HAWC2Farm, an extension of HAWC2 that can model multiple wind turbines with shared mooring lines. We apply the new modeling capabilities to simulate two 15 MW floating wind turbines on spar floaters with shared mooring lines. We consider two different sites and we identify and compare the natural frequencies and mode shapes of the shared mooring designs with those of an individual moored turbine. Furthermore, we investigate the influence of design parameters on the systems’ natural frequencies and we show that it is possible for a shared mooring design to achieve similar characteristics as a single turbine design. Finally, we test the response of the shared mooring design in steady wind and regular waves and find that the surge displacement of the upstream turbine and its mooring line loads are considerably larger compared to the single turbine case.
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Chen, Weimin, Shuangxi Guo, Yilun Li et Yijun Shen. « Impacts of Mooring-Lines Hysteresis on Dynamic Response of Spar Floating Wind Turbine ». Energies 14, no 8 (9 avril 2021) : 2109. http://dx.doi.org/10.3390/en14082109.
Texte intégralRésumé :
Floating wind turbines often experience larger-amplitude motions caused by wind and ocean wave loads, while mooring-lines, such as catenary and taut mooring-lines, make the structure configurations along with an analysis of the global response more complicated compared to a fixed support foundation. Moreover, the restoring performance of dynamic mooring-lines exhibits a significant hysteresis behavior, and this hysteresis behavior may have profound impacts on the structural response of floating wind turbines under environmental loads. In this study, using the coupled finite element method, a dynamic simulation model is developed to study the motion responses of a spar floating wind turbine under consideration of mooring-lines hysteresis. In order to consider large-amplitude motion and nonlinear behaviors of catenary mooring-lines, a FEM (finite element method) model is developed based on a combination of 3D nonlinear beam elements and the super-element approach, and the interaction between mooring-lines and seabed is also included. Using our FEM numerical simulations, firstly, the restoring performance of mooring-lines and its hysteresis behavior are studied. Then, the motion responses, e.g., the displacements of the spar float undergoing various wave loads, are examined. The numerical results show that: the restoring stiffness of mooring-lines exhibits significant hysteresis behavior, and the restoring force is directionally dependent. Due to the hysteresis of restoring performance, for a case of regular wave conditions, little change of the spar surge in a steady-state is seen; however, for a case of extreme wave loads, the motion response gets about 14.4% smaller, compared with the quasi-static cases.
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Cevasco, D., M. Collu, CM Rizzo et M. Hall. « On mooring line tension and fatigue prediction for offshore vertical axis wind turbines : A comparison of lumped mass and quasi-static approaches ». Wind Engineering 42, no 2 (20 mars 2018) : 97–107. http://dx.doi.org/10.1177/0309524x18756962.
Texte intégralRésumé :
Despite several potential advantages, relatively few studies and design support tools have been developed for floating vertical axis wind turbines. Due to the substantial aerodynamics differences, the analyses of vertical axis wind turbine on floating structures cannot be easily extended from what have been already done for horizontal axis wind turbines. Therefore, the main aim of the present work is to compare the dynamic response of the floating offshore wind turbine system adopting two different mooring dynamics approaches. Two versions of the in-house aero-hydro-mooring coupled model of dynamics for floating vertical axis wind turbine (FloVAWT) have been used, employing a mooring quasi-static model, which solves the equations using an energetic approach, and a modified version of floating vertical axis wind turbine, which instead couples with the lumped mass mooring line model MoorDyn. The results, in terms of mooring line tension, fatigue and response in frequency have been obtained and analysed, based on a 5 MW Darrieus type rotor supported by the OC4-DeepCwind semisubmersible.
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Weller, S. D., L. Johanning, P. Davies et S. J. Banfield. « Synthetic mooring ropes for marine renewable energy applications ». Renewable Energy 83 (novembre 2015) : 1268–78. http://dx.doi.org/10.1016/j.renene.2015.03.058.
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Eskilsson, Claes, Johannes Palm, Pär Johannesson et Guilherme Moura Paredes. « Sensitivity analysis of extreme loads acting on a point-absorbing wave energy converter ». International Marine Energy Journal 5, no 1 (18 juin 2022) : 91–101. http://dx.doi.org/10.36688/imej.5.91-101.
Texte intégralRésumé :
There are many uncertainties associated with the estimation of extreme loads acting on a wave energy converter (WEC). In this study we perform a sensitivity analysis of extreme loads acting on the Uppsala University (UU) WEC concept. The UU WEC consists of a bottom-mounted linear generator that is connected to a surface buoy with a taut mooring line. The maximum stroke length of the linear generator is enforced by end-stop springs. Initially, a Variation Mode and Effect Analysis (VMEA) was carried out in order to identify the largest input uncertainties. The system was then modelled in the time-domain solver WEC-SIM coupled to the dynamic mooring solver Moody. A sensitivity analysis was made by generating a surrogate model based on polynomial chaos expansions, which rapidly evaluates the maximum loads on the mooring line and the end-stops. The sensitivities are ranked using the Sobol index method. We investigated two sea states using equivalent regular waves (ERW) and irregular wave (IRW) trains. We found that the ERW approach significantly underestimate the maximum loads. Interestingly, the ERW predicted wave height and period as the most important parameters for the maximum mooring tension, whereas the tension in IRW was most sensitive to the drag coefficient of the surface buoy. The end-stop loads were most sensitive to the PTO damping coefficient.
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Liu, Baolong, et Jianxing Yu. « Effect of Mooring Parameters on Dynamic Responses of a Semi-Submersible Floating Offshore Wind Turbine ». Sustainability 14, no 21 (27 octobre 2022) : 14012. http://dx.doi.org/10.3390/su142114012.
Texte intégralRésumé :
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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Kardakaris, Kimon, Dimitrios N. Konispoliatis et Takvor H. Soukissian. « Theoretical evaluation of the power efficiency of a moored hybrid floating platform for wind and wave energy production in the Greek seas ». AIMS Geosciences 9, no 1 (2023) : 153–83. http://dx.doi.org/10.3934/geosci.2023009.
Texte intégralRésumé :
<abstract> <p>In this study, an extreme value analysis of wind and wave parameters is presented for three specific locations in the Greek seas that are known to be advantageous in terms of joint power production (both offshore wind and wave) and bathymetric conditions. The analysis is conducted via the Peak-Over-Threshold method, examining wind speed, significant wave height and peak wave period data from the ERA5 reanalysis dataset. Moreover, a multi-purpose floating platform suitable for offshore energy production is presented, which combines wind and wave energy resources exploitation and can be adequately utilized at the selected locations. The analysis is built to incorporate the solutions of the diffraction, motion-dependent and pressure-dependent radiation problems around the floating structure, along with the mooring line and wind turbine (WT) characteristics. Subsequently, a coupled hydro-aero-elastic analysis was performed in the frequency domain, while a dynamic analysis was conducted in order to evaluate the mooring characteristics. Lastly, offshore wind output and absorbed wave energy values were estimated, and different types of mooring systems were compared in terms of efficiency. It has been concluded that the wind energy capacity factor is higher than 50% in all the examined locations, and by the mooring system comparison, the tension-leg platform (TLP) represents the best-case scenario for wave energy absorption.</p> </abstract>
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Wang, Yan Gang, Xing Hua Tong, Lin Sen Zhu et Yong Liu. « The Design and Calculation of the Mooring System in Floating Body with Rope Wheel Device ». Applied Mechanics and Materials 361-363 (août 2013) : 378–81. http://dx.doi.org/10.4028/www.scientific.net/amm.361-363.378.
Texte intégralRésumé :
Floating body with rope wheel structure is a new wave energy device, which is simple and low cost. Mooring system is the key technology of this device, which is use to limit the horizontal motion of the floating structure in the designated area. In this paper, potential energy theory has been used in the process of design and calculation of mooring system. Using the result of calculation, the motion of the floating body has been simulated numerically.
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Chen, Cheng-Tsung, Jaw-Fang Lee et Chun-Han Lo. « Mooring Drag Effects in Interaction Problems of Waves and Moored Underwater Floating Structures ». Journal of Marine Science and Engineering 8, no 3 (25 février 2020) : 146. http://dx.doi.org/10.3390/jmse8030146.
Texte intégralRésumé :
In contrast to either considering structures with full degrees of freedom but with wave force on mooring lines neglected or with wave scattering and radiation neglected, in this paper, a new analytic solution is presented for wave interaction with moored structures of full degrees of freedom and with wave forces acting on mooring lines considered. The linear potential wave theory is applied to solve the wave problem. The wave fields are expressed as superposition of scattering and radiation waves. Wave forces acting on the mooring lines are calculated using the Morison equation with relative motions. A coupling formulation among water waves, underwater floating structure, and mooring lines are presented. The principle of energy conservation, as well as numerical results, are used to verify the present solution. With complete considerations of interactions among waves and moored structures, the characteristics of motions of the structure, the wave fields, and the wave forces acting on the mooring lines are investigated.
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Wu, Jo-Ti, Jiahn-Horng Chen, Ching-Yeh Hsin et Forng-Chen Chiu. « Dynamics of The FKT System with Different Mooring Lines ». Polish Maritime Research 26, no 1 (1 mars 2019) : 20–29. http://dx.doi.org/10.2478/pomr-2019-0003.
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Abstract To harness the endless hydrokinetic energy of the Kuroshio current, the joint research team of the National Taiwan University and the National Taiwan Ocean University has developed a floating Kuroshio turbine (FKT) system in Taiwan. In normal operation, the system floats at a certain small depth from the ocean surface to reduce the wave effects and take advantage of faster current speeds. In the present study, the effect of the mooring line on the system dynamics is investigated computationally. Two different auxiliary mooring line designs and, for each design, three different common mooring lines (polyester ropes of neutral buoyancy, iron chains, and 6×19 wires ropes with wire core) are examined. The study makes use of several commercial and in-house packages, integrated to find various coefficients. It is found that the mooring line, the auxiliary mooring line design, and the gravity centre can have a significant effect on system fluctuations in normal operation if the combination of these factors is not properly matched.
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Ji, Chun-yan, Zhi-ming Yuan et Ming-lu Chen. « Study on a new mooring system integrating catenary with taut mooring ». China Ocean Engineering 25, no 3 (27 août 2011) : 427–40. http://dx.doi.org/10.1007/s13344-011-0035-4.
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Levachev, S. N., I. M. Galimov, V. V. Filippov, A. G. Nemolochnov et N. A. Zubachev. « Mooring Structure with Rigid Anchorage ». Power Technology and Engineering 52, no 6 (mars 2019) : 652–56. http://dx.doi.org/10.1007/s10749-019-01007-x.
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Huang, Wei-Hua, et Ray-Yeng Yang. « Water Depth Variation Influence on the Mooring Line Design for FOWT within Shallow Water Region ». Journal of Marine Science and Engineering 9, no 4 (12 avril 2021) : 409. http://dx.doi.org/10.3390/jmse9040409.
Texte intégralRésumé :
The objective of this paper was to present the modeling and optimization of mooring lines for floating offshore wind turbines (FOWT) located in various water depths from 50 m to 100 m in Taiwan western offshore areas. A semi-submersible floating wind turbine system is considered based on Offshore Code Comparison Collaborative Continuation (OC4) DeepCwind platform with the National Renewable Energy Laboratory (NREL) offshore 5-MW baseline wind turbine. The mooring lines proposed consist of a catenary mooring with studless chains. Three nominal sizes of the mooring chain links are taken into account with diameters of 95 mm, 115 mm and 135 mm. According to this configuration, a total of five mooring designs for different water depths (i.e., 50 m, 60 m, 70 m, 80 m, 100 m) are analyzed according to the rules and regulations of the two certification institutions, Det Norske Veritas (DNV) and American Petroleum Institute (API). Considering ultimate limit state (ULS), fatigue limit state (FLS) and maximum operating sea state (MOSS) based on a typhoon with a 50-year return period and current with a 10-year return period, 25-year design life, as well as 1-year return period, respectively, long-term predictions of breaking strength, fatigue and stability are performed. The software OrcaFlex version 10.3 d is used to simulate and design the mooring lines. The obtained results show that the shallow mooring design of 50 m water depth case presents the heaviest chains among the other water depths, increasing their mooring costs. On the other hand, the 100 m water design has much longer mooring lines, making this parameter the cost driving one. Thus, the minimum mooring cost range is from 60 m to 80 m water depth.
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Pease, F. T., M. D. Burns et M. C. Chen. « Storm Quick-Disconnect Mooring System ». Journal of Energy Resources Technology 107, no 4 (1 décembre 1985) : 467–72. http://dx.doi.org/10.1115/1.3231220.
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Severe storms such as hurricanes or typhoons can cause significant damage to offshore drilling rigs. Drillships, due to their high mobility, can flee severe storms after disconnecting from the mooring system. This paper presents a newly developed quick-connect/disconnect mooring system to permit the drilling rig to move off station quickly. The application of such a quick-connect/disconnect mooring system to the turret-moored drillship is presented.
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Ramp, Steven R., Yiing Jang Yang, Ching-Sang Chiu, D. Benjamin Reeder et Frederick L. Bahr. « Observations of shoaling internal wave transformation over a gentle slope in the South China Sea ». Nonlinear Processes in Geophysics 29, no 3 (8 juillet 2022) : 279–99. http://dx.doi.org/10.5194/npg-29-279-2022.
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Abstract. Four oceanographic moorings were deployed across the South China Sea continental slope near 21.85∘ N, 117.71∘ E, from 30 May to 18 July 2014 for the purpose of observing high-frequency nonlinear internal waves (NLIWs) as they shoaled across a rough, gently sloping bottom. Individual waves required just 2 h to traverse the array and could thus easily be tracked from mooring to mooring. In general, the amplitude of the incoming NLIWs tracked the fortnightly tidal envelope in the Luzon Strait; they lagged by 48.5 h and were smaller than the waves previously observed to the southwest near the Dongsha Plateau. Two types of waves, a waves and b waves, were observed, with the b waves always leading the a waves by 6–8 h. Most of the NLIWs were remotely generated, but a few of the b waves formed locally via convergence and breaking at the leading edge of the upslope-propagating internal tide. Waves incident upon the moored array with amplitude less than 50 m and energy less than 100 MJ m−1 propagated adiabatically upslope with little change of form. Larger waves formed packets via wave dispersion. For the larger waves, the kinetic energy flux decreased sharply upslope between 342 and 266 m, while the potential energy flux increased slightly, causing an increasing ratio of potential-to-kinetic energy as the waves shoaled. None of the waves met the criteria for convective breaking. The results are in rough agreement with recent theory and numerical simulations of shoaling waves.
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Yang, Wei, Hao Wei et Liang Zhao. « Parametric Subharmonic Instability of the Semidiurnal Internal Tides at the East China Sea Shelf Slope ». Journal of Physical Oceanography 50, no 4 (avril 2020) : 907–20. http://dx.doi.org/10.1175/jpo-d-19-0163.1.
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AbstractOn the basis of measurements from an observing mooring system, the observational evidence of parametric subharmonic instability (PSI) that transfers energy from semidiurnal internal tides (ITs) to the subharmonic waves at the East China Sea continental shelf slope is presented for the first time. Although the mooring station is very close to the energetic semidiurnal IT generation site, about 76% of the observed shear variance is contained in the near-inertial band, which is found to have comparable upward- and downward-propagating energy components. Bispectra and bicoherence estimates further confirm the occurrence of PSI transferring energy from the low-mode M2 ITs (vertical wavelength of ~1000 m) to high-mode subharmonic waves (vertical wavelength of ~200 m). The calculated energy transfer rate reveals an averaged net value of ~5 × 10−9 W kg−1. Strong temporal variation of is found that is not exactly in phase with the semidiurnal energy flux. After looking into the local vorticity fields, it is strongly suggested that the varying background relative vorticity associated with the evolving Kuroshio has modified the efficiency of PSI at the mooring location through changing the local effective inertial frequency.
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Zheng, Xing, Tianyin Zhang, Zhenhong Hu et Gang Ma. « Study on Characteristics and Optimal Layout of Components in Shallow Water Mooring System of Floating Wind Turbine ». Applied Sciences 12, no 19 (9 octobre 2022) : 10137. http://dx.doi.org/10.3390/app121910137.
Texte intégralRésumé :
Offshore wind energy resources far exceed those on land. However, the increase in water depth of the continental shelf in China’s sea area slows down as the distance from the shore increases. In view of the characteristics of China’s sea, how to optimize the design of mooring systems to adapt to the water depth conditions in China’s waters and to resist the harsh sea conditions is one of the major problems encountered in the development of floating wind turbines. In this paper, the 5MW-OC4 semi-submersible floating wind turbine is taken as the research object, and the frequency domain and time domain calculation of the floating wind turbine are carried out by using SESAM software under the water depth of 40 m in the Bohai Sea. By comparing the motion response and tension of catenary and tension mooring floating wind turbine. The mooring system is optimized by combining the buoy and clump weight. The results show that the catenary mooring mode is more suitable for the floating wind turbine under shallow water conditions. Mooring accessories used in combination have the same effect on the overall response of the floating wind turbine as changing the same mooring parameters when used alone, but the effect of changing the mooring parameters on the performance optimization of the mooring system is more obvious when used in combination, and a reasonable combination of accessories can significantly change the overall characteristics of the floating system and affect the safety and cost of the system.
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Zhou, Yiming, Sensen Feng, Xiaojiang Guo, Feng Tian, Xu Han, Wei Shi et 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 (21 février 2023) : 464. http://dx.doi.org/10.3390/jmse11030464.
Texte intégralRésumé :
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.