scholarly journals Effect of Roughness of Mussels on Cylinder Forces from a Realistic Shape Modelling

2021 ◽  
Vol 9 (6) ◽  
pp. 598
Author(s):  
Antoine Marty ◽  
Franck Schoefs ◽  
Thomas Soulard ◽  
Christian Berhault ◽  
Jean-Valery Facq ◽  
...  
Keyword(s):  
Marine Species ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Mooring Lines ◽  
Shape Modelling ◽  
Offshore Wind Turbines ◽  
Specific Effects ◽  
Hydrodynamic Loading ◽  
Floating Offshore Wind Turbines ◽  
Realistic Shape

After a few weeks, underwater components of offshore structures are colonized by marine species and after few years this marine growth can be significant. It has been shown that it affects the hydrodynamic loading of cylinder components such as legs and braces for jackets, risers and mooring lines for floating units. Over a decade, the development of Floating Offshore Wind Turbines highlighted specific effects due to the smaller size of their components. The effect of the roughness of hard marine growth on cylinders with smaller diameter increased and the shape should be representative of a real pattern. This paper first describes the two realistic shapes of a mature colonization by mussels and then presents the tests of these roughnesses in a hydrodynamic tank where three conditions are analyzed: current, wave and current with wave. Results are compared to the literature with a similar roughness and other shapes. The results highlight the fact that, for these realistic roughnesses, the behavior of the rough cylinders is mainly governed by the flow and not by their motions.

scholarly journals Proposal and Performance Study of a Novel Mooring System with Six Mooring Lines for Spar-Type Offshore Wind Turbines

2021 ◽  
Vol 11 (24) ◽  
pp. 11665
Author(s):  
Shi Liu ◽  
Yi Yang ◽  
Chao Wang ◽  
Yuangang Tu
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Offshore Wind Turbine ◽  
Mooring System ◽  
Mooring Lines ◽  
Included Angle ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

Spar-type floating offshore wind turbines commonly vibrate excessively when under the coupling impact of wind and wave. The wind turbine vibration can be controlled by developing its mooring system. Thus, this study proposes a novel mooring system for the spar-type floating offshore wind turbine. The proposed mooring system has six mooring lines, which are divided into three groups, with two mooring lines in the same group being connected to the same fairlead. Subsequently, the effects of the included angle between the two mooring lines on the mooring-system’s performance are investigated. Then, these six mooring lines are connected to six independent fairleads for comparison. FAST is utilized to calculate wind turbine dynamic response. Wind turbine surge, pitch, and yaw movements are presented and analyzed in time and frequency domains to quantitatively evaluate the performances of the proposed mooring systems. Compared with the mooring system with six fairleads, the mooring system with three fairleads performed better. When the included angle was 40°, surge, pitch, and yaw movement amplitudes of the wind turbine reduced by 39.51%, 6.8%, and 12.34%, respectively, when under regular waves; they reduced by 56.08%, 25.00%, and 47.5%, respectively, when under irregular waves. Thus, the mooring system with three fairleads and 40° included angle is recommended.

scholarly journals Hydro-Servo-Aero-Elastic Analysis of Floating Offshore Wind Turbines

Fluids ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 200
Author(s):  
Dimitris I. Manolas ◽  
Vasilis A. Riziotis ◽  
George P. Papadakis ◽  
Spyros G. Voutsinas
Keyword(s):  
Structural Dynamics ◽  
Wind Turbines ◽  
Computational Cost ◽  
Physical Models ◽  
Offshore Wind ◽  
Mooring Lines ◽  
Rotor Aerodynamics ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Free Wake

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.

Evaluation of a Hybrid Representation to Model the Wind Turbine, Platform and Mooring Lines in the Analysis of Floating Offshore Wind Turbines

2021 ◽  
Author(s):  
Eloi Daniel de Araujo Neto ◽  
William Rodriguez ◽  
Fabr\xedcio Nogueira Corr\xeaa ◽  
Beatriz De Souza Leite Pires De Lima ◽  
Breno Pinheiro Jacob ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Offshore Wind ◽  
Mooring Lines ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

scholarly journals Fatigue Assessment of Moorings for Floating Offshore Wind Turbines by Advanced Spectral Analysis Methods

2021 ◽  
Vol 10 (1) ◽  
pp. 37
Author(s):  
Vincenzo Piscopo ◽  
Antonio Scamardella ◽  
Giovanni Battista Rossi ◽  
Francesco Crenna ◽  
Marta Berardengo
Keyword(s):  
Spectral Analysis ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Time Domain ◽  
Offshore Wind ◽  
Stress Process ◽  
Mooring Lines ◽  
Offshore Wind Turbines ◽  
Analysis Methods ◽  
Floating Offshore Wind Turbines

The fatigue assessment of mooring lines for floating offshore wind turbines represents a challenging issue not only for the reliable design of the stationkeeping system but also for the economic impact on the installation and maintenance costs over the entire lifetime of the offshore wind farm. After a brief review about the state-of-art, the nonlinear time-domain hydrodynamic model of floating offshore wind turbines moored by chain cables is discussed. Subsequently, the assessment of the fatigue damage in the mooring lines is outlined, focusing on the combined-spectrum approach. The relevant fatigue parameters, due to the low- and wave-frequency components of the stress process, are estimated by two different methods. The former is based on the time-domain analysis of the filtered stress process time history. The latter, instead, is based on the spectral analysis of the stress process by two advanced methods, namely the Welch and Thomson ones. Subsequently, a benchmark study is performed, assuming as reference floating offshore wind turbine the OC4-DeepCWind semisubmersible platform, equipped with the 5 MW NREL wind turbine. The cumulative fatigue damage is determined for eight load conditions, including both power production and parked wind turbine situations. A comparative analysis between time-domain and spectral analysis methods is also performed. Current results clearly show that the endorsement of advanced spectral analysis methods can be helpful to improve the reliability of the fatigue life assessment of mooring lines.

scholarly journals DESIGN OF A 3D PHYSICAL AND NUMERICAL EXPERIMENT ON FLOATING OFF-SHORE WIND TURBINES

2012 ◽  
Vol 1 (33) ◽  
pp. 67 ◽  
Author(s):  
Giuseppe Roberto Tomasicchio ◽  
Elvira Armenio ◽  
Felice D'Alessandro ◽  
Nuno Fonseca ◽  
Spyros A. Mavrakos ◽  
...  
Keyword(s):  
Wind Turbines ◽  
Preliminary Test ◽  
Offshore Wind ◽  
Mooring Lines ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Wave Basin ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Smoothed Particle Hydrodynamics Method

The knowledge of the behavior of floating offshore wind turbines (W/T) under wave and/or wind action remains one of the most difficult challenges in offshore engineering which is mostly due to the highly non-linear response of the structure. The present study describes the design process of a 3D physical experiment to investigate the behavior of the most promising structure technology of floating W/T: spar buoy (SB) and tension leg platform (TLP) under different meteo conditions. In order to properly design the two W/T models, the following topics have been analyzed: mooring lines, mass distribution, appropriate scaling factor and data relative to the geometrical characteristics, wave basin dimensions and wind and waves conditions. In addition, the Smoothed Particle Hydrodynamics method (SPH) (Monaghan 1994) has been considered to simulate the 3D behavior of a floating offshore W/T. In particular, the SPH, calibrated and verified on the basis of the experimental observations, may represent a reliable tool for preliminary test of changes in the floater geometry.

Experimental Study of the Stationkeeping of a Floater Using Passive Flapping Flat Plates in Waves

2019 ◽  
Author(s):  
Woo-Lim Sim ◽  
Hyunkyoung Shin ◽  
Rupesh Kumar
Keyword(s):  
Experimental Study ◽  
Three Dimensional ◽  
Offshore Wind ◽  
Flat Plates ◽  
Mooring Lines ◽  
Ongoing Research ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Flapping Foils ◽  
The University

Abstract To effectively use the resources of marine environments, it is necessary to consider the deep and remote parts of the ocean. Stationkeeping of floating offshore wind turbines (FOWTs) mainly relies on mooring lines[1][2]. However, current mooring lines have structural and economical limitations for applications in extreme sea environments. The University of Ulsan is conducting ongoing research to develop a new economical stationkeeping system that can maintain the position of a FOWT in the deep sea using passive flapping foils. This paper describes an experimental study of the stationkeeping of actual structures based on the above-mentioned investigations and suggested directions to supplement the deficiencies in stationkeeping systems using passive flapping foils. This experiment was carried out in the three-dimensional “Widetank” and in actual sea conditions, focusing on the drift of a floater in the surge direction.

scholarly journals Investigation of Hydrodynamic Forces for Floating Offshore Wind Turbines on Spar Buoys and Tension Leg Platforms with the Mooring Systems in Waves

2019 ◽  
Vol 9 (3) ◽  
pp. 608 ◽  
Author(s):  
Yu-Hsien Lin ◽  
Shin-Hung Kao ◽  
Cheng-Hao Yang
Keyword(s):  
Wind Turbines ◽  
Time Domain ◽  
Simulation System ◽  
Offshore Wind ◽  
Modular System ◽  
Mooring System ◽  
Mooring Lines ◽  
Offshore Wind Turbines ◽  
Motion Responses ◽  
Floating Offshore Wind Turbines

This study aims to develop a modularized simulation system to estimate dynamic responses of floating Offshore Wind Turbines (OWTs) based on the concepts of spar buoy and Tension Leg Platform (TLP) corresponding with two typical mooring lines. The modular system consists of the hydrodynamic simulator based the Cummins time domain equation, the Boundary Element Method (BEM) solver based on the 3D source distribution method, and an open-source visualization software ParaView to analyze the interaction between floating OWTs and waves. In order to realize the effects of mooring loads on the floating OWTs, the stiffness and damping matrices are applied to the quasi-static mooring system. The Response Amplitude Operators (RAOs) are compared between our predicted results and other published data to verify the modularized simulation system and understand the influence of mooring load on the motion responses in regular or irregular waves. It is also demonstrated that the quasi-static mooring system is applicable to different types of mooring lines as well as determining real-time motion responses. Eventually, wave load components at the resonance frequencies of different motion modes for selected floating OWTs would be present in the time domain.

scholarly journals Study of motion of spar-type floating wind turbines in waves with effect of gyro moment at inclination

2012 ◽  
Vol 9 (1) ◽  
pp. 67-79 ◽  
Author(s):  
N. Mostafa ◽  
M. Murai ◽  
R. Nishimura ◽  
O. Fujita ◽  
Y. Nihei
Keyword(s):  
Wind Turbines ◽  
Offshore Structures ◽  
Moment Of Inertia ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Scale Model ◽  
Water Tank ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Marine Engineering

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

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