Journal cover Journal topic
Wind Energy Science The interactive open-access journal of the European Academy of Wind Energy
https://doi.org/10.5194/wes-2017-41
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research articles
26 Oct 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Wind Energy Science (WES).
Application of a Monte Carlo Procedure for Probabilistic Fatigue Design of Floating Offshore Wind Turbines
Kolja Müller and Po Wen Cheng Stuttgart Wind Energy @ Institute of Aircraft Design, University of Stuttgart, Germany
Abstract. Fatigue load assessment of floating offshore wind turbines poses new challenges on the feasibility of numerical procedures. Due to the increased sensitivity of the considered system with respect to the environmental conditions from wind and ocean, the application of common procedures used for fixed-bottom structures results in either inaccurate simulation results or hard-to-quantify conservatism in the system design. Monte Carlo based sampling procedures provide a more realistic approach to deal with the large variation of the environmental conditions, although basic randomization has shown slow convergence. Specialized sampling methods allow efficient coverage of the complete design space, resulting in faster convergence and hence a reduced number of required simulations. In this study, a quasi-random sampling approach based on Sobol’ sequences is applied to select representative events for the determination of the lifetime damage. This is calculated applying Monte-Carlo integration, using subsets of a resulting total of 16 200 coupled time-domain simulations performed with the simulation code FAST. The considered system is the DTU 10 MW reference turbine installed on the LIFES50+ OO-Star Wind Floater Semi 10 MW floating platform. Statistical properties of the considered environmental parameters (i.e. wind speed, wave height and wave period) are determined based on the measurement data from Gulf of Maine, USA. Convergence analyses show that it is sufficient to perform around 200 simulations in order to reach less than 10 % uncertainty of lifetime fatigue damage equivalent loading. Complementary in-depth investigation is performed focusing on the load sensitivity and the impact of outliers. Recommendations for the implementation of the proposed methodology in the design process are also provided.

Citation: Müller, K. and Cheng, P. W.: Application of a Monte Carlo Procedure for Probabilistic Fatigue Design of Floating Offshore Wind Turbines, Wind Energ. Sci. Discuss., https://doi.org/10.5194/wes-2017-41, in review, 2017.
Kolja Müller and Po Wen Cheng
Kolja Müller and Po Wen Cheng
Kolja Müller and Po Wen Cheng

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Short summary
A new method is presented to assess the lifetime fatigue loading on a floating offshore wind turbine accurately. This is typically challenging due to the many different combinations of environmental conditions which need to be considered (e.g. wind speed, wave height, current speed, wind/wave directions, etc.) which may lead to excessive simulation effort. With the presented method, it is possible to consider different environmental conditions while keeping the number of simulations at a minimum
A new method is presented to assess the lifetime fatigue loading on a floating offshore wind...
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