Experimental Flow-Induced Motions of a FOWT Semi-Submersible Type (OC4 Phase II Floater)

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Rodolfo T. Gonçalves ◽  
Maria E. F. Chame ◽  
Leandro S. P. Silva ◽  
Arjen Koop ◽  
Shinichiro Hirabayashi ◽  
...  
Keyword(s):  
Phase Ii ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Circular Column ◽  
Deep Waters ◽  
Floating Offshore Wind Turbines ◽  
Floating System ◽  
Cable Systems ◽  
Column Design

Abstract Flow-induced motions (FIM) are an issue for floating offshore structures, such as multi-column platforms, as the phenomenon can decrease the fatigue life of the mooring, riser, and cable systems. The new concept of floating offshore wind turbines (FOWT) have a multi-column design that may be subjected to FIM. In the past, FIM was studied mainly for Oil & Gas platforms installed in deep waters. However, the FIM phenomenon of FOWT has been insufficiently explored. To rectify this, model tests were performed for the semisubmersible (SS) floating system design developed for the DeepCwind project (Offshore Code Comparison Collaboration Continuation (OC4) phase II). This paper will investigate the presence of FIM and show its importance in the design process of FOWT. Three different incidence angles of the current were tested, namely, 0, 90, and 180 deg. For each heading, 30 reduced velocities were tested, across the range 8000 < Re < 70,000. The results showed amplitudes in the transverse direction of around 70% of the diameter of the platform column, which is similar to those observed for deep-draft (DD) SS with circular columns. Note that these amplitude values are larger for a floater with a circular column, than for a platform with square columns. The results showed that as FIM occurred for this specific FOWT SS, its effect has to be considered in the mooring system and electric cable design.

Experimental Study on Flow-Induced Motions (FIM) of a Floating Offshore Wind Turbine Semi-Submersible Type (OC4 Phase II Floater)

2019 ◽  
Author(s):  
Rodolfo T. Gonçalves ◽  
Maria E. F. Chame ◽  
Leandro S. P. Silva ◽  
Arjen Koop ◽  
Shinichiro Hirabayashi ◽  
...  
Keyword(s):  
Phase Ii ◽  
Transverse Direction ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Offshore Wind Turbines ◽  
Deep Waters ◽  
New Concepts ◽  
Floating Offshore Wind Turbines ◽  
Floating System ◽  
Cable Systems

Abstract Flow-Induced Motions (FIM) is an issue for multi-column platforms, and the phenomenon can decrease the fatigue life of the mooring, riser, and cable systems. In the past, FIM was studied mainly for platforms installed in deep waters. The new concepts of Floating Offshore Wind Turbines (FOWT) have multi-column design and may therefore observe FIM. However, FOWTs have been installed in shallow water and, in this case, the FIM remains insufficiently investigated. To address this issue, FIM model tests were performed for the – Semisubmersible (SS) Floating System design developed for the DeepCwind project (OC4 Phase II). The goal of this paper is to investigate the presence of FIM for this type of system to show the importance of FIM in the design of FOWT. Three different incidence angles of the current were tested, namely 0, 90 and 180 degrees. For each heading, thirty reduced velocities were tested. The results showed amplitudes in the transverse direction of around 70% of the diameter of the platform column, which is similar to the ones observed for the deep-draft (DD) SS with circular columns and larger than for the platforms with square columns. The results showed that FIM was present for this specific FOWT SS investigated and that it may thus be essential to consider when designing the mooring system, as an increment in the total cost of the platform may make the system economically unfeasible. When extrapolating the results for the full-scale configuration, the FIM synchronization occurred for current velocities from 0.5m/s up to 1.2m/s, and the maximum nondimensional nominal amplitudes for the motions in the transverse direction reached 70% of the external column diameter.

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 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

scholarly journals Parametric study of dynamic inter-array cable systems for floating offshore wind turbines

2020 ◽  
Vol 15 (1) ◽  
pp. 16-25
Author(s):  
Manuel U. T. Rentschler ◽  
Frank Adam ◽  
Paulo Chainho ◽  
Kilian Krügel ◽  
Pedro C. Vicente
Keyword(s):  
Wind Turbines ◽  
Parametric Study ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Cable Systems

Pitch Angle Control of Floating Offshore Wind Turbines by H∞ Control

2014 ◽  
Vol 134 (8) ◽  
pp. 1096-1103 ◽  
Author(s):  
Sho Tsujimoto ◽  
Ségolène Dessort ◽  
Naoyuki Hara ◽  
Keiji Konishi
Keyword(s):  
Wind Turbines ◽  
Pitch Angle ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

scholarly journals Maintenance Planning of Offshore Wind Turbine Using Condition Monitoring Information

2009 ◽  
Author(s):  
Jose´ G. Rangel-Rami´rez ◽  
John D. So̸rensen
Keyword(s):  
Condition Monitoring ◽  
Wind Turbines ◽  
Wind Farm ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Maintenance Planning ◽  
Offshore Wind Turbines ◽  
Inspection And Maintenance ◽  
Monitoring Information

Deterioration processes such as fatigue and corrosion are typically affecting offshore structures. To “control” this deterioration, inspection and maintenance activities are developed. Probabilistic methodologies represent an important tool to identify the suitable strategy to inspect and control the deterioration in structures such as offshore wind turbines (OWT). Besides these methods, the integration of condition monitoring information (CMI) can optimize the mitigation activities as an updating tool. In this paper, a framework for risk-based inspection and maintenance planning (RBI) is applied for OWT incorporating CMI, addressing this analysis to fatigue prone details in welded steel joints at jacket or tripod steel support structures for offshore wind turbines. The increase of turbulence in wind farms is taken into account by using a code-based turbulence model. Further, additional modes t integrate CMI in the RBI approach for optimal planning of inspection and maintenance. As part of the results, the life cycle reliabilities and inspection times are calculated, showing that earlier inspections are needed at in-wind farm sites. This is expected due to the wake turbulence increasing the wind load. With the integration of CMI by means Bayesian inference, a slightly change of first inspection times are coming up, influenced by the reduction of the uncertainty and harsher or milder external agents.

scholarly journals Impact of Typhoons on Floating Offshore Wind Turbines: A Case Study of Typhoon Mangkhut

2021 ◽  
Vol 9 (5) ◽  
pp. 543
Author(s):  
Jiawen Li ◽  
Jingyu Bian ◽  
Yuxiang Ma ◽  
Yichen Jiang
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Safety Evaluation ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Motion Response ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Coupling Motion

A typhoon is a restrictive factor in the development of floating wind power in China. However, the influences of multistage typhoon wind and waves on offshore wind turbines have not yet been studied. Based on Typhoon Mangkhut, in this study, the characteristics of the motion response and structural loads of an offshore wind turbine are investigated during the travel process. For this purpose, a framework is established and verified for investigating the typhoon-induced effects of offshore wind turbines, including a multistage typhoon wave field and a coupled dynamic model of offshore wind turbines. On this basis, the motion response and structural loads of different stages are calculated and analyzed systematically. The results show that the maximum response does not exactly correspond to the maximum wave or wind stage. Considering only the maximum wave height or wind speed may underestimate the motion response during the traveling process of the typhoon, which has problems in guiding the anti-typhoon design of offshore wind turbines. In addition, the coupling motion between the floating foundation and turbine should be considered in the safety evaluation of the floating offshore wind turbine under typhoon conditions.

scholarly journals Performance Analysis on the Use of Oscillating Water Column in Barge-Based Floating Offshore Wind Turbines

Mathematics ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 475
Author(s):  
Payam Aboutalebi ◽  
Fares M’zoughi ◽  
Izaskun Garrido ◽  
Aitor J. Garrido
Keyword(s):  
Wind Turbines ◽  
Positive Impact ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Water Columns ◽  
Numerical Tools ◽  
Oscillating Water Columns ◽  
The Given ◽  
The Waves

Undesired motions in Floating Offshore Wind Turbines (FOWT) lead to reduction of system efficiency, the system’s lifespan, wind and wave energy mitigation and increment of stress on the system and maintenance costs. In this article, a new barge platform structure for a FOWT has been proposed with the objective of reducing these undesired platform motions. The newly proposed barge structure aims to reduce the tower displacements and platform’s oscillations, particularly in rotational movements. This is achieved by installing Oscillating Water Columns (OWC) within the barge to oppose the oscillatory motion of the waves. Response Amplitude Operator (RAO) is used to predict the motions of the system exposed to different wave frequencies. From the RAOs analysis, the system’s performance has been evaluated for representative regular wave periods. Simulations using numerical tools show the positive impact of the added OWCs on the system’s stability. The results prove that the proposed platform presents better performance by decreasing the oscillations for the given range of wave frequencies, compared to the traditional barge platform.

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