Extreme response analysis for a jacket-type offshore wind turbine using environmental contour method

2014 ◽  
pp. 5597-5604 ◽  
Author(s):  
Qinyuan Li ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Contour Method ◽  
Offshore Wind Turbine ◽  
Response Analysis ◽  
Extreme Response

scholarly journals Effect of Wind Turbulence on Extreme Load Analysis of an Offshore Wind Turbine

2019 ◽  
Author(s):  
Xiaolu Chen ◽  
Zhiyu Jiang ◽  
Qinyuan Li ◽  
Ye Li
Keyword(s):  
Wind Turbine ◽  
Turbulence Intensity ◽  
Environmental Conditions ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Contour Method ◽  
Offshore Wind Turbine ◽  
Extreme Response ◽  
Wind Turbulence ◽  
The Impact

Abstract Evaluation of dynamic responses under extreme environmental conditions is important for the structural design of offshore wind turbines. Previously, a modified environmental contour method has been proposed to estimate extreme responses. In the method, the joint distribution of environmental variables near the cut-out wind speed is used to derive the critical environmental conditions for a specified return period, and the turbulence intensity (TI) of wind is assumed to be a deterministic value. To address more realistic wind conditions, this paper considers the turbulence intensity as a stochastic variable and investigates the impact on the modified environmental contour. Aerodynamic simulations are run over a range of mean wind speeds at the hub height from 9–25 m/s and turbulence levels between 9%–15%. Dynamic responses of a monopile offshore wind turbine under extreme conditions were studied, and the importance of considering the uncertainties associated with wind turbulence is highlighted. A case of evaluating the extreme response for 50-year environmental contour is given as an example of including TI as an extra variant in environmental contour method. The result is compared with traditional method in which TI is set as a constant of 15%. It shows that taking TI into consideration based on probabilistic method produces a lower extreme response prediction.

Short-term extreme response analysis of a jacket supporting an offshore wind turbine

Wind Energy ◽  
2012 ◽  
Vol 17 (1) ◽  
pp. 87-104 ◽  
Author(s):  
Nilanjan Saha ◽  
Zhen Gao ◽  
Torgeir Moan ◽  
Arvid Naess
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Response Analysis ◽  
Short Term ◽  
Extreme Response

scholarly journals Extended Environmental Contour Methods for Long-Term Extreme Response Analysis of Offshore Wind Turbines1

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Xiaolu Chen ◽  
Zhiyu Jiang ◽  
Qinyuan Li ◽  
Ye Li ◽  
Nianxin Ren
Keyword(s):  
Turbulence Intensity ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Contour Method ◽  
Offshore Wind Turbine ◽  
Response Analysis ◽  
Modified Method ◽  
Extreme Response ◽  
Wind Turbulence

Abstract Environmental contour method is an efficient method for predicting the long-term extreme response of offshore structures. The traditional environmental contour is obtained using the joint distribution of mean wind speed, significant wave height, and spectral peak period. To improve the accuracy of traditional environmental contour method, a modified method was proposed considering the non-monotonic aerodynamic behavior of offshore wind turbines. Still, the modified method assumes constant wind turbulence intensity. In this paper, we extend the existing environmental contour methods by considering the wind turbulence intensity as a stochastic variable. The 50-year extreme responses of a monopile-based offshore wind turbine are compared using the extended environmental contour methods and the full long-term method. It is found that both the environmental contour method and the modified environmental contour method, with the wind turbulence intensity included as an individual variable, give more accurate predictions compared with those without. Using the full long-term method as a benchmark, this extended approach could reduce the nonconservatism of the environmental contour method and conservatism of the modified environmental contour method. This approach is effective under wind-dominated or combined wind-wave loading conditions, but may not be as important for wave-dominated conditions.

Extreme Response Prediction of Offshore Wind Turbine Using Inverse Reliability Technique

2015 ◽  
Author(s):  
D. Karmakar ◽  
C. Guedes Soares
Keyword(s):  
Wind Turbine ◽  
Bending Moment ◽  
Response Prediction ◽  
Computational Effort ◽  
Offshore Wind ◽  
Contour Method ◽  
Offshore Wind Turbine ◽  
Floating Wind Turbine ◽  
Extreme Response ◽  
Design Loads

In the present study, the environmental contour method is applied for predicting out-of-plane bending moment loads at the blade root and tower base moment loads for 5MW offshore floating wind turbine of spar-type, DeepCWind and WindFloat semi-submersible floater configuration. FAST code is used to simulate the wind conditions for various return periods and a brief comparison on the design loads of the floating wind turbine for I-D, 2-D and 3-D environmental contour method is analyzed. In addition, a brief comparison of design loads with the spar-type, DeepCWind and WindFloat semi-submersible floater is discussed. The study is helpful to improve the turbine design load estimates and is useful in predicting accurate long-term design loads for wind turbines without requiring excessive computational effort.

Prediction of Short-Term Extreme Response of Floating Offshore Wind Turbine Under Storm Condition

2020 ◽  
Author(s):  
Zhi Zong ◽  
Guanqing Hu ◽  
Yichen Jiang ◽  
Li Zou
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Offshore Wind Turbine ◽  
Frequency Interval ◽  
Short Term ◽  
Two Phase ◽  
Floating Offshore Wind Turbine ◽  
Motion Responses ◽  
Extreme Response

Abstract To predict the short-term motion responses of floating offshore wind turbine under extreme wind-wave excitation, a numerical model based on the two-phase flow finite volume method was developed. In this paper, uni-directional irregular waves composed of 100 cosine waves with equal frequency interval were simulated by the wave forcing technique, resulting in the measured spectrum in accordance with the target spectrum. Then, a 100-seconds wave segment containing the maximum wave height was selected for fully coupled dynamic analysis of the OC4-DeepCwind system in CFD, and the results were compared with those of FAST under the same wind and wave sea state. It was found that the motion responses of heave and pitch motion responses predicted by two methods agree well. The second-order slow drift force generated in CFD led to the difference in surge motion. The predicted sway, roll, and yaw motions by these two methods were also compared. In addition, significant differences between two methods’ predictions on mooring tension were found.

scholarly journals Sensitivity Analysis of a Bottom Fixed Offshore Wind Turbine Using the Environmental Contour Method

2019 ◽  
Author(s):  
David Barreto ◽  
Abdolmajid Moghtadaei ◽  
Madjid Karimirad ◽  
Arturo Ortega
Keyword(s):  
Wind Turbine ◽  
Wave Height ◽  
Environmental Conditions ◽  
Stochastic Dynamics ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Contour Method ◽  
Exceedance Probability ◽  
Offshore Wind Turbine ◽  
Peak Period

Abstract In the field of stochastic dynamics of marine structures, environmental conditions play a vital role. Considering wind and waves as random processes, determining the environmental parameters which correspond to an annual exceedance probability for a certain structural concept is of vital importance for the respective assessment of the loads and their effects. The accuracy in predicting the conditions, especially those corresponding to the sea, is of a great relevance when a probabilistic design is performed in order to ensure the structural integrity of an offshore wind turbine. In particular, models are not always completely perfect and accurate data is not always available. The Environmental Contour Method (ECM), which is based on the IFORM methodology, is one of the most popular methods in the offshore industry when determining the environmental conditions, for a given annual exceedance probability, is required. The ECM allows analysing proper sea states for operational and extreme conditions with lower computational efforts than the most accurate method (Full Long-Term Analysis). In the present study, effects of progressive variations (uncertainties) of the sea states parameters (i.e. significant wave height, spectral peak period) on the dynamic response of a Monopile Wind Turbine (NREL 5MW) are analysed. Two operative conditions are considered: rated wind and cut-out wind speed. In each case, the 50-year environmental contour (EC) is plotted for a site located in the North Sea. Some sea states are selected from the EC (base cases) and then derived cases with percentage variations are generated. All the cases are simulated in FAST (NREL) and the standard deviations of the time series are compared with its respective values of base cases. The results for the dynamic responses at mudline (e.g. overturning moments and shear forces) are presented as the most important parameters governing the design of the monopile. In this analysis, the wave height shows more influence on the response variation percentage than the peak period. This work shows the importance of accurately setting up the input parameters and their impact on the calculation of the dynamic responses.

At-Sea Experiment on Durability and Residual Strength of Polyester Rope for Mooring of Floating Wind Turbine

2019 ◽  
Author(s):  
Tomoaki Utsunomiya ◽  
Iku Sato ◽  
Koji Tanaka
Keyword(s):  
Wind Turbine ◽  
Residual Strength ◽  
Offshore Wind ◽  
Synthetic Fiber ◽  
Floating Body ◽  
Mooring Line ◽  
Offshore Wind Turbine ◽  
Response Analysis ◽  
Initial State ◽  
Characteristic Values

Abstract When using synthetic fiber rope as a mooring line of a floating body such as floating offshore wind turbine (FOWT), it is necessary to carry out characteristic test and to grasp well about strength, stiffness, durability against monotonic and cyclic loadings. In this research, we have made characteristics test of polyester rope based on ISO. Next, based on the obtained characteristic values (mass, stiffness, strength, etc.), the dynamic response analysis of the floating body-mooring system was carried out and the mooring design was carried out. It was actually operated as a floating body mooring line for about 1 year. During the operation period, no abnormality was found, nor appearance damage occurred. After completion of operation for 1 year, the polyester rope was collected and residual strength test was carried out. As a result, no serious deterioration situation such as infiltration of marine organisms or fracture of the strands due to wear between fibers was observed at all. On the other hand, with respect to durability, it was found that the strength reduction was 2.9% from the initial state with respect to the breaking strength.

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