Joint Description Methods of Wind and Waves for the Design of Offshore Wind Turbines

For the design of offshore wind energy structures against an ultimate limit state or fatigue, the combination of wind and wave loads that are likely to occur simultaneously during the design life of the wind turbine must be estimated. This complex task involves different wind/wave models, load-calculation methods and statistical analysis of simultaneous extreme wind and wave conditions. Reliable and realistic methods for the assessment of the service life of an offshore wind energy converter under combined wind and wave loads are necessary. However, the current design guidelines provide little information on how to model the wind and wave correlation. This paper investigates several approaches for obtaining the required wind-wave correlation. Statistical correlation methods with jointly measured wind and wave data, manual wave forecasting methods, numerical sea state hindcast, and joint probability model data have been compared with each other as well as to simultaneously measured wind and wave data from the FINO research platform in the German Bight of the North Sea. The advantages and drawbacks of each method are discussed. A straightforward application of the manual wave forecast methods gives good results for wave height prediction, but only the average wind-wave behavior would be represented if unsorted wind data is taken into account. The correlation methods based upon equal probabilities can be a first approximation only if the distribution of mean wind speeds and significant wave weights is available. Under storm conditions, wave heights are underestimated. The numerical hindcast gives realistic results, but is demanding in terms of preparation and computational time. The joint distribution model is a fast approach to set up a realistic model to describe the local wind and wave conditions, but only if synchronously recorded wind and wave data is available over large time histories.

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  • English

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  • Accession Number: 01142481
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Oct 25 2009 10:37PM