scholarly journals Fatigue Life Assessment for Power Cables in Floating Offshore Wind Turbines

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3096
Author(s):  
Mohsen Sobhaniasl ◽  
Francesco Petrini ◽  
Madjid Karimirad ◽  
Franco Bontempi
Keyword(s):  
Fatigue Life ◽  
Wind Waves ◽  
Numerical Approach ◽  
Life Assessment ◽  
Offshore Wind ◽  
Numerical Code ◽  
Offshore Wind Turbine ◽  
Commercial Code ◽  
Floating Offshore Wind Turbines ◽  
Combined Action

In this paper, a procedure is proposed to determine the fatigue life of the electrical cable connected to a 5 MW floating offshore wind turbine, supported by a spar-buoy at a water depth of 320 m, by using a numerical approach that takes into account site-specific wave and wind characteristics. The effect of the intensity and the simultaneous actions of waves and wind are investigated and the outcomes for specific cable configurations are shown. Finally, the fatigue life of the cable is evaluated. All analyses have been carried out using the Ansys AQWA computational code, which is a commercial code for the numerical investigation of the dynamic response of floating and fixed marine structures under the combined action of wind, waves and current. Furthermore, this paper applies the FAST NREL numerical code for comparison with the ANSYS AQWA results.

Calibration of Long-Term Time-Domain Load Generation for Fatigue Life Assessment of Offshore Wind Turbine

2017 ◽  
Author(s):  
Bryan Nelson ◽  
Yann Quéméner ◽  
Tsung-Yueh Lin ◽  
Hsin-Haou Huang ◽  
Chi-Yu Chien
Keyword(s):  
Fatigue Life ◽  
Wind Turbine ◽  
Fatigue Damage ◽  
Time Domain ◽  
Hot Spot ◽  
Life Assessment ◽  
Offshore Wind ◽  
Wind Loads ◽  
Offshore Wind Turbine

This study evaluated, by time-domain simulations, the fatigue life of the jacket support structure of a 3.6 MW wind turbine operating in Fuhai Offshore Wind Farm. The long-term statistical environment was based on a preliminary site survey that served as the basis for a convergence study for an accurate fatigue life evaluation. The wave loads were determined by the Morison equation, executed via the in-house HydroCRest code, and the wind loads on the wind turbine rotor were calculated by an unsteady BEM method. A Finite Element model of the wind turbine was built using Beam elements. However, to reduce the time of computation, the hot spot stress evaluation combined FE-derived Closed-Form expressions of the nominal stresses at the tubular joints and stress concentration factors. Finally, the fatigue damage was assessed using the Rainflow Counting scheme and appropriate SN curves. Based on a preliminary sensitivity study of the fatigue damage prediction, an optimal load setting of 60-min short-term environmental conditions with one-second time steps was selected. After analysis, a sufficient fatigue strength was identified, but further calculations involving more extensive long-term data measurements are required in order to confirm these results. Finally, this study highlighted the sensitivity of the fatigue life to the degree of fluctuation (standard deviation) of the wind loads, as opposed to the mean wind loads, as well as the importance of appropriately orienting the jacket foundations according to prevailing wind and wave conditions.

Hydrodynamic Forces and Pressure Loads on Heave Plates for Semi-Submersible Floating Offshore Wind Turbines: A Case Study

2014 ◽  
Author(s):  
Carlos Lopez-Pavon ◽  
Carlos A. Garrido-Mendoza ◽  
Antonio Souto-Iglesias
Keyword(s):  
Structural Design ◽  
Dynamic Pressure ◽  
Hydrodynamic Forces ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Preliminary Design ◽  
Offshore Wind Turbines ◽  
Commercial Code ◽  
Floating Offshore Wind Turbines

Hydrodynamic forces on heave plates for a semi-submersible floating offshore wind turbine are discussed in this paper. Results from experiments in which added mass and damping coefficients have been measured are presented. A model which allows the fitting of a plain plate and the real reinforced one has been built. The experimental campaign comprised as well the direct measurement of dynamic pressure on the heave plates, important for the heave plates structural design. Numerical simulations have been conducted both with a frequency domain panel method and a RANS CFD commercial code. Results have been compared with literature and consistent nondimensionalizations have been sought so that such results can be useful for preliminary design purposes.

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.

Coupled Dynamic Analysis for Multi-Unit Floating Offshore Wind Turbine in Maximum Operational and Survival Conditions

2015 ◽  
Author(s):  
H. K. Jang ◽  
H. C. Kim ◽  
M. H. Kim ◽  
K. H. Kim
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Time Domain ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Random Waves ◽  
Mooring Lines ◽  
Floating Offshore Wind Turbine ◽  
Coupled Dynamic Analysis ◽  
Floating Offshore Wind Turbines

Numerical tools for a single floating offshore wind turbine (FOWT) have been developed by a number of researchers, while the investigation of multi-unit floating offshore wind turbines (MUFOWT) has rarely been performed. Recently, a numerical simulator was developed by TAMU to analyze the coupled dynamics of MUFOWT including multi-rotor-floater-mooring coupled effects. In the present study, the behavior of MUFOWT in time domain is described through the comparison of two load cases in maximum operational and survival conditions. A semi-submersible floater with four 2MW wind turbines, moored by eight mooring lines is selected as an example. The combination of irregular random waves, steady currents and dynamic turbulent winds are applied as environmental loads. As a result, the global motion and kinetic responses of the system are assessed in time domain. Kane’s dynamic theory is employed to formulate the global coupled dynamic equation of the whole system. The coupling terms are carefully considered to address the interactions among multiple turbines. This newly developed tool will be helpful in the future to evaluate the performance of MUFOWT under diverse environmental scenarios. In the present study, the aerodynamic interactions among multiple turbines including wake/array effect are not considered due to the complexity and uncertainty.

Verification Study of CFD Simulation of Semi-Submersible Floating Offshore Wind Turbine Under Regular Waves

2021 ◽  
Author(s):  
Yu Wang ◽  
Hamn-Ching Chen ◽  
Guilherme Vaz ◽  
Simon Mewes
Keyword(s):  
Cfd Simulation ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Regular Waves ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Spatial Convergence ◽  
Goal Response ◽  
Computational Fluid Dynamics Cfd ◽  
Response Amplitude Operators

Abstract Utilization of Computational Fluid Dynamics (CFD) codes to perform hydrodynamic analysis of Floating Offshore Wind Turbines (FOWTs) is increasing recently. However, verification studies of the simulations that quantifying numerical uncertainties and permitting a detailed validation in a next phase is often disregarded. In this work, a verification study of CFD simulations of a semi-submersible FOWT design under regular waves is performed. To accomplish this goal, Response Amplitude Operators (RAOs) are derived from the computational results of the heave, surge and pitch motions. Four grids with different grid sizes with a constant refinement ratio are generated for verification of spatial convergence. Three different time increments are paired with each grid for verification of temporal convergence. The verification study is performed by estimation of the numerical errors and uncertainties using procedures proposed by Eca and Hoekstra [1].

Optimizing the Cost and Reliability of Shared Anchors in an Array of Floating Offshore Wind Turbines

2021 ◽  
Author(s):  
Michael Devin ◽  
Bryony DuPont ◽  
Spencer Hallowell ◽  
Sanjay Arwade
Keyword(s):  
Optimization Algorithm ◽  
System Reliability ◽  
Failure Modes ◽  
The United States ◽  
Offshore Wind ◽  
Bayesian Optimization ◽  
Maintenance Cost ◽  
Offshore Wind Turbine ◽  
Trade Offs ◽  
Floating Offshore Wind Turbines

Abstract Commercial floating offshore wind projects are expected to emerge in the United States by the end of this decade. Currently, however, high costs for the technology limit its commercial viability, and a lack of data regarding system reliability heightens project risk. This work presents an optimization algorithm to examine the trade-offs between cost and reliability for a floating offshore wind array that uses shared anchoring. Combining a multivariable genetic algorithm with elements of Bayesian optimization, the optimization algorithm selectively increases anchor strengths to minimize the added costs of failure for a large floating wind farm in the Gulf of Maine under survival load conditions. The algorithm uses an evaluation function that computes the probability of mooring system failure, then calculates the expected maintenance costs of a failure via a Monte Carlo method. A cost sensitivity analysis is also performed to compare results for a range of maintenance cost profiles. The results indicate that virtually all of the farm's anchors are strengthened in the minimum cost solution. Anchor strength is in- creased between 5-35% depending on farm location, with anchor strength nearest the export cable being increased the most. The optimal solutions maintain a failure probability of 1.25%, demonstrating the trade-off point between cost and reliability. System reliability was found to be particularly sensitive to changes in turbine costs and downtime, suggest- ing further research into floating offshore wind turbine failure modes in extreme loading conditions could be particularly impactful in reducing project uncertainty.

Evaluating the Coupledness of the Aerodynamics and Hydrodynamics on the Estimation of Fatigue Damage Equivalent Load for a Floating Offshore Wind Platform

2018 ◽  
Author(s):  
Samuel Kanner ◽  
Bingbin Yu
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Environmental Conditions ◽  
Offshore Wind ◽  
Coupled Analysis ◽  
Offshore Wind Turbine ◽  
Wave Conditions ◽  
Equivalent Load ◽  
The Waves

In this research, the estimation of the fatigue life of a semi-submersible floating offshore wind platform is considered. In order to accurately estimate the fatigue life of a platform, coupled aerodynamic-hydrodynamic simulations are performed to obtain dynamic stress values. The simulations are performed at a multitude of representative environmental states, or “bins,” which can mimic the conditions the structure may endure at a given site, per ABS Floating Offshore Wind Turbine Installation guidelines. To accurately represent the variety of wind and wave conditions, the number of environmental states can be of the order of 103. Unlike other offshore structures, both the wind and wave conditions must be accounted for, which are generally considered independent parameters, drastically increasing the number of states. The stress timeseries from these simulations can be used to estimate the damage at a particular location on the structure by using commonly accepted methods, such as the rainflow counting algorithm. The damage due to either the winds or the waves can be estimated by using a frequency decomposition of the stress timeseries. In this paper, a similar decoupled approach is used to attempt to recover the damages induced from these coupled simulations. Although it is well-known that a coupled, aero-hydro analysis is necessary in order to accurately simulate the nonlinear rigid-body motions of the platform, it is less clear if the same statement could be made about the fatigue properties of the platform. In one approach, the fatigue damage equivalent load is calculated independently from both scatter diagrams of the waves and a rose diagram of the wind. De-coupled simulations are performed to estimate the response at an all-encompassing range of environmental conditions. A database of responses based on these environmental conditions is constructed. The likelihood of occurrence at a case-study site is used to compare the damage equivalent from the coupled simulations. The OC5 platform in the Borssele wind farm zone is used as a case-study and the damage equivalent load from the de-coupled methods are compared to those from the coupled analysis in order to assess these methodologies.

Fatigue life assessment of three offshore wind turbines

2016 ◽  
pp. 742-747 ◽  
Author(s):  
W. Weijtjens ◽  
N. Noppe ◽  
T. Verbelen ◽  
C. Devriendt ◽  
A. Iliopoulos
Keyword(s):  
Fatigue Life ◽  
Wind Turbines ◽  
Life Assessment ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Fatigue Life Assessment

scholarly journals Safety Evaluation of the Combined Load for Offshore Wind Turbine Suction Foundation Installed on Sandy Soil

2021 ◽  
Vol 33 (5) ◽  
pp. 195-202
Author(s):  
Jeong Seon Park
Keyword(s):  
Wind Turbine ◽  
Sandy Soil ◽  
Wind Waves ◽  
Safety Evaluation ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Element Analysis ◽  
Combined Load ◽  
Combined Loads ◽  
Moment Load

Offshore wind turbine (OWT) receive a combined vertical-horizontal- moment load by wind, waves, and the structure’s own weight. In this study, the bearing capacity for the combined load of the suction foundation of OWT installed on the sandy soil was calculated by finite element analysis. In addition, the stress state of the soil around the suction foundation was analyzed in detail under the condition that a combined load was applied. Based on the results of the analyses, new equations are proposed to calculate the horizontal and moment bearing capacities as well as to define the capacity envelopes under general combined loads.

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