Effect of foundation modelling on the fatigue lifetime of a monopile-based offshore wind turbine

Aasen, Steffen; Page, Ana M.; Skau, Kristoffer Skjolden; Nygaard, Tor Anders

doi:10.5194/wes-2-361-2017

Cited by 30 publications

(10 citation statements)

References 35 publications

(38 reference statements)

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“…The difference in DELs between different foundation models are moderate for an operating turbine, but large for mean winds below cut‐in and above cut‐out speeds when the turbine is idling and damping is low. This points to the importance of consideration of soil damping for more economical design …”

Section: Resultsmentioning

confidence: 99%

“…Most recently, Markou and Kaynia developed a procedure for extending the non‐linear static p‐y springs to cyclic loading and implemented a procedure for limiting the damping generated by the hysteretic loops in the springs. To assess the importance of soil‐pile modelling and damping, Aasen et al carried out a parametric study in which they used four different models for the simulation of the monopile of an OWT. The first model, which is a common model used in the industry, comprised nonlinear elastic springs that do not dissipate energy; the second model was a linear elastic stiffness matrix at the pile head; the third model was similar to the second one with the addition of damping, and the last model consisted of uncoupled nonlinear horizontal and rotational springs at the pile head represented by a series of elasto‐plastic springs as proposed by Iwan .…”

Section: Introductionmentioning

confidence: 99%

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Effect of foundation type and modelling on dynamic response and fatigue of offshore wind turbines

Løken

Kaynia

2019

Wind Energy

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This paper presents dynamic response and fatigue analyses of several bottom‐mounted offshore wind turbine (OWT) models, simulated in the aero‐hydro‐servo‐elastic simulation tool FAST. The distinction between the models is the foundations, which are modelled with different methods, concepts, and dimensions. The US National Renewable Energy Laboratory has developed a 5‐MW reference turbine supported on a monopile, the NREL 5MW, which was used as a reference model in this paper. The paper presents the implementation and comparison of two different foundation modeling methods, referred to as the simplified apparent fixity method and the improved apparent fixity method. Furthermore, sensitivity analyses of different monopile dimensions were performed, followed by sensitivity analyses of suction caisson foundations of different dimensions. The final part of the paper presents fatigue analyses for the foundation models considered in this study subjected to 17 load cases. Fatigue damage, fatigue life, and damage equivalent loads were calculated, as well as the relative fatigue contribution from each load case.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of foundation type and modelling on dynamic response and fatigue of offshore wind turbines

Løken

Kaynia

2019

Wind Energy

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“…For these cases, different wave and wind conditions, and different angles of misalignment between wind and waves were encountered. Idling cases were chosen as the response of the entire OWT is more influenced by the foundation performance during idling cases than during production cases [5].…”

Section: Foundation Modellingmentioning

confidence: 99%

“…Variations in the foundation stiffness lead to changes in the natural frequencies of the OWT. This can bring the natural frequencies of the structure closer to the environmental and mechanical excitation frequencies, increasing the fatigue damage and consequently reducing the designed fatigue lifetime [5]. In addition, the damping contribution from the foundation helps to attenuate the dynamic amplification of the response, especially during idling conditions when aerodynamic damping is relatively small.…”

Section: Introductionmentioning

confidence: 99%

Impact of foundation modelling in offshore wind turbines: Comparison between simulations and field data

et al. 2019

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The design of Offshore Wind Turbines (OWTs) relies on integrated simulation tools capable of predicting the system dynamic characteristics and the coupled loads and responses. Despite all efforts to develop accurate integrated models, these often fail to reproduce the measured natural frequencies, partly due to the modelling of the foundation. Several foundation models and calibration approaches have been proposed and compared with small or large scale field tests, where only the soil and the foundation are included. However, there is a lack of more integral validation where the interaction between the foundation and the structure is taken into account. The paper investigates the impact of the foundation model and calibration approach on the simulated response of a monopile-based OWT installed in the North Sea by comparing simulations and full-scale field data. The OWT structure and the environmental actions are implemented in the aero-servo-hydro-elastic code 3DFloat. Two foundation models and two calibration approaches are evaluated. The results indicate that, with a conceptually correct foundation model and a realistic calibration, it is possible to match the measured natural frequency and predict accurate fatigue loads. More accurate predicted loads will reduce uncertainties in the estimated fatigue lifetime and therefore reduce risk in the design.

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“…These loads include wind, wave, and underwater current. These different forms of environmental loads combined with turbine operation condition, soil-structure interaction and flexible member dynamics make it difficult to accurately quantify the complicated dynamics and predict the system behavior of OWT (Dnvgl, 2016;Aasen et al, 2017;Bhattacharya, 2019). Wind and wave-current loads are the main external loads applied on operational OWTs, which may lead to a great overturning moment and shear force at its foundation and supporting structure (Alagan Chella et al, 2012;Stansby et al, 2013;Morató et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Conceptual Study of a Real-Time Hybrid Simulation Framework for Monopile Offshore Wind Turbines Under Wind and Wave Loads

Song

Sun

Zuo

et al. 2020

Front. Built Environ.

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As an attractive renewable energy source, offshore wind plants are becoming increasingly popular for energy production. However, the performance assessment of offshore wind turbine (OWT) structure is a challenging task due to the combined wind-wave loading and difficulties in reproducing such loading conditions in laboratory. Real-time hybrid simulation (RTHS), combining physical testing and numerical simulation in real-time, offers a new venue to study the structural behavior of OWTs. It overcomes the scaling incompatibilities in OWT scaled model testing by replacing the rotor components with an actuation system, driven by an aerodynamic simulation tool running in real-time. In this study, a RTHS framework for monopile OWTs is proposed. A set of sensitivity analyses is carried out to evaluate the feasibility of this RTHS framework and determine possible tolerances on its design. By simulating different scaling laws and possible error contributors (delays and noises) in the proposed framework, the sensitivity of the OWT responses to these parameters are quantified. An example using a National Renewable Energy Lab (NREL) 5-MW reference OWT system at 1:25 scale is simulated in this study to demonstrate the proposed RTHS framework and sensitivity analyses. Three different scaling laws are considered. The sensitivity results show that the delays in the RTHS framework significantly impact the performance on the response evaluation, higher than the impact of noises. The proposed framework and sensitivity analyses presented in this study provides important information for future implementation and further development of the RTHS technology for similar marine structures.

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Effect of foundation modelling on the fatigue lifetime of a monopile-based offshore wind turbine

Cited by 30 publications

References 35 publications

Effect of foundation type and modelling on dynamic response and fatigue of offshore wind turbines

Effect of foundation type and modelling on dynamic response and fatigue of offshore wind turbines

Impact of foundation modelling in offshore wind turbines: Comparison between simulations and field data

Conceptual Study of a Real-Time Hybrid Simulation Framework for Monopile Offshore Wind Turbines Under Wind and Wave Loads

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