scholarly journals Reliability Updating of Offshore Wind Substructures by Use of Digital Twin Information

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5859
Author(s):  
Dawid Augustyn ◽  
Martin D. Ulriksen ◽  
John D. Sørensen
Keyword(s):  
Wind Turbine ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Structural Reliability ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Loading ◽  
Soil Stiffness ◽  
Digital Twins ◽  
Fatigue Damage Accumulation

This paper presents a probabilistic framework for updating the structural reliability of offshore wind turbine substructures based on digital twin information. In particular, the information obtained from digital twins is used to quantify and update the uncertainties associated with the structural dynamics and load modeling parameters in fatigue damage accumulation. The updated uncertainties are included in a probabilistic model for fatigue damage accumulation used to update the structural reliability. The updated reliability can be used as input to optimize decision models for operation and maintenance of existing structures and design of new structures. The framework is exemplified based on two numerical case studies with a representative offshore wind turbine and information acquired from previously established digital twins. In this context, the effect of updating soil stiffness and wave loading, which constitute two highly uncertain and sensitive parameters, is investigated. It is found that updating the soil stiffness significantly affects the reliability of the joints close to the mudline, while updating the wave loading significantly affects the reliability of the joints localized in the splash zone. The increased uncertainty related to virtual sensing, which is employed to update wave loading, reduces structural reliability.

Key Contributors to Lifetime Accumulated Fatigue Damage in an Offshore Wind Turbine Support Structure

2017 ◽  
Author(s):  
Emil Smilden ◽  
Erin E. Bachynski ◽  
Asgeir J. Sørensen
Keyword(s):  
Wind Turbine ◽  
Fatigue Damage ◽  
Control Strategies ◽  
Time Domain Analysis ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Loads ◽  
Support Structure ◽  
Wear And Tear ◽  
Collateral Effects

A simulation study is performed to identify the key contributors to lifetime accumulated fatigue damage in the support-structure of a 10 MW offshore wind turbine placed on a monopile foundation in 30 m water depth. The relative contributions to fatigue damage from wind loads, wave loads, and wind/wave misalignment are investigated through time-domain analysis combined with long-term variations in environmental conditions. Results show that wave loads are the dominating cause of fatigue damage in the support structure, and that environmental condtions associated with misalignment angle > 45° are insignificant with regard to the lifetime accumulated fatigue damage. Further, the results are used to investigate the potential of event-based use of control strategies developed to reduce fatigue loads through active load mitigation. Investigations show that a large reduction in lifetime accumulated fatigue damage is possible, enabling load mitigation only in certain situations, thus limiting collateral effects such as increased power fluctuations, and wear and tear of pitch actuators and drive-train components.

Analysis of the Fatigue Life of Offshore Wind Turbine Generators Under Combined Ice- and Aerodynamic Loading

2014 ◽  
Author(s):  
Hayo Hendrikse ◽  
Frank W. Renting ◽  
Andrei V. Metrikine
Keyword(s):  
Wind Turbine ◽  
Phenomenological Models ◽  
Fatigue Damage ◽  
Offshore Wind Turbine ◽  
Superposition Method ◽  
Design Standards ◽  
Combined Analysis ◽  
Aerodynamic Loading ◽  
Ice Load ◽  
Fatigue Damage Accumulation

A modelled wind turbine generator subjected to combined ice- and aerodynamic loading is analyzed with the focus on its fatigue lifetime. A comparison is made between the prediction of a combined analysis, taking both ice- and wind loads into account simultaneously, and a superposition analysis, computing the response of the structure as a result of ice and wind loading separately. The accumulated fatigue damage is computed considering different descriptions of the ice load. Prescribed ice load curves from current design standards, as well as phenomenological models for the prediction of dynamic ice-structure interaction are employed. Results show that the superposition method underpredicts the accumulated fatigue damage in the range of frequency lock-in, but only when phenomenological models, which are more advanced than those recommended by the design standards, are used to model the ice load. Furthermore the predicted fatigue damage computed using the design standards for the description of the ice load is found to be much larger than that resulting from the application of the phenomenological models. It is concluded that the combined analysis is desired when phenomenological models are applied. Furthermore, improvement of the predictive capabilities of such models might ultimately lead to a reduction of the predicted fatigue damage accumulation of the combined ice- and aerodynamic load case, as compared to the current prescribed methods in standards.

Probabilistic Analysis of the Fatigue Life of Offshore Wind Turbine Structures

2020 ◽  
Author(s):  
Abraham Nispel ◽  
Stephen Ekwaro-Osire ◽  
João Paolo Dias
Keyword(s):  
Fatigue Life ◽  
Wind Turbine ◽  
Structural Reliability ◽  
Research Question ◽  
Limit State ◽  
Fatigue Loading ◽  
Offshore Wind ◽  
Design Parameters ◽  
Offshore Wind Turbine ◽  
Loading Conditions

Abstract The structural response of the main components of offshore wind turbines (OWTs) is considerably sensitive to amplification as their excitation frequencies approach the natural frequency of the structure. Furthermore, uncertainties present in the loading conditions, soil and structural properties highly influence the dynamic response of the OWT. In most cases, the cost of the structure reaches around 30% of the entire OWT because conservative design approaches are employed to ensure its reliability. As a result, this study aims to address the following research question: can the structural reliability of OWT under fatigue loading conditions be predicted more consistently? The specific aims are to (1) establish the design parameters that most impact the fatigue life, (2) determine the probability distributions of the design parameters, and (3) predict the structural reliability. An analytical model to determine the fatigue life of the structure under 15 different loading conditions and two different locations were developed. Global sensitivity analysis was used to establish the more important design parameters. Also, a systematic uncertainty quantification (UQ) scheme was employed to model the uncertainties of model input parameters based on their available information. Finally, the framework used reliability analysis to consistently determine the system probability of failure of the structure based on the fatigue limit state design criterion. The results show high sensitivity for parameters usually considered as deterministic values in design standards. Additionally, it is shown that applying systematic UQ produces a better approximation of the fatigue life under uncertainty and more accurate estimations of the structural reliability. Consequently, more reliable and robust structural designs may be achieved without the need for overestimating the offshore wind turbine response.

Analysis of Fatigue Damage for Offshore Wind Turbine Substructure

2013 ◽  
Vol 454 ◽  
pp. 7-14
Author(s):  
Bin Wang ◽  
Ying Li ◽  
Jin Ping Luo ◽  
Dan Shan Wang ◽  
Sheng Xiao Zhao
Keyword(s):  
Wind Turbine ◽  
Fatigue Damage ◽  
Probability Distributions ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Direction ◽  
Wave Load ◽  
Fatigue Load ◽  
Linear Superposition ◽  
Loading Direction

Based on the probability distributions of wind direction and wave direction, the fatigue load is applied to the offshore wind turbine structure according to the actual environmental loading direction. The deterministic fatigue damage due to the wind load and the spectrum fatigue damage due to the wave load are calculated, respectively. Then, the total fatigue damage of the offshore wind turbine structure is obtained by the linear superposition. Compared with the results that the fatigue damage of the offshore wind turbine structure is computed under fatigue loads exerted in single direction, the results of omnidirectional fatigue analysis are more reasonable.

A Fast and Practical Method for Predicting the Fatigue Life of Offshore Wind Turbine Jacket Support Structures

2017 ◽  
Author(s):  
Chaoshuai Han ◽  
Yongliang Ma ◽  
Xianqiang Qu ◽  
Peijiang Qin ◽  
Binbin Qiu
Keyword(s):  
Fatigue Life ◽  
Wind Turbine ◽  
Fatigue Damage ◽  
Time Domain ◽  
Practical Method ◽  
Computational Effort ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Loads ◽  
Support Structures

Fatigue assessment is a very important part in the design process of offshore wind turbine support structures subjected to wind and wave loads. Fully coupled time domain simulations due to wind and wave loads can potentially provide reliable fatigue predictions, however, it will take high computational effort to carry out fatigue analysis of the simultaneous wind and wave response of the support structure in time domain. For convenience and reducing computational efforts, a fast and practical method is proposed for predicting the fatigue life of offshore wind turbine jacket support structures. Wind induced fatigue is calculated in the time domain using ANSYS based on rainflow counting, and wave induced fatigue is computed in frequency domain using SACS based on a linear spectral analysis. Fatigue damage of X-joints and K-joints under combined environmental loads of wind and wave is estimated by using the proposed method. To verify the accuracy of the proposed formula, fatigue damage based on time domain rainflow cycle counting is calculated and can be considered as a reference. It is concluded that the proposed method provides reasonable fatigue damage predictions and can be adopted for evaluating the combined fatigue damage due to wind and wave loads in offshore wind turbine.

scholarly journals Effects of Second-Order Hydrodynamics on the Dynamic Responses and Fatigue Damage of a 15 MW Floating Offshore Wind Turbine

2021 ◽  
Vol 9 (11) ◽  
pp. 1232
Author(s):  
Xuan Mei ◽  
Min Xiong
Keyword(s):  
Wind Turbine ◽  
Fatigue Damage ◽  
Second Order ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Extreme Condition ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Floating Offshore Wind Turbine ◽  
The Cost

In order to investigate the effects of second-order hydrodynamic loads on a 15 MW floating offshore wind turbine (FOWT), this study employs a tool that integrates AQWA and OpenFAST to conduct fully coupled simulations of the FOWT subjected to wind and wave loadings. The load cases covering normal and extreme conditions are defined based on the met-ocean data observed at a specific site. The results indicate that the second-order wave excitations activate the surge mode of the platform. As a result, the surge motion is increased for each of the examined load case. In addition, the pitch, heave, and yaw motions are underestimated when neglecting the second-order hydrodynamics under the extreme condition. First-order wave excitation is the major contributor to the tower-base bending moments. The fatigue damage of the tower-base under the extreme condition is underestimated by 57.1% if the effect of second-order hydrodynamics is ignored. In addition, the accumulative fatigue damage over 25 years at the tower-base is overestimated by 16.92%. Therefore, it is suggested to consider the effects of second-order wave excitations of the floating platform for the design of the tower to reduce the cost of the FOWT.

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