NewGUST, MODELLING OF EXTREME GUSTS FOR DESIGN CALCULATIONS

Objectives

For design load calculations of wind turbines it is necessary to determine the fatigue loads as well as the extreme loads. Up to now simple deterministic and coherent gusts have been used to determine the extreme response. The shape, amplitude and duration specified for these discrete events remain rather arbitrary and largely unvalidated. This is in contrast to the fatigue analysis, which conventionally rely on a synthetic stochastic wind field reflecting the stochastic properties of natural turbulence.
The main objective of the here presented NewGust project is to achieve a realistic and verified description of extreme gusts based on the (stochastic) properties of wind.

Technical Approach

In essence the NewGust method, describes a way to combine a stochastic turbulence field (as used for fatigue analysis) and a well defined deterministic gust shape (which can be theoretically derived) in such a way that a realistic extreme gust is obtained.

The project approach can be divided into the following steps:
1)      Experimental verification of the shape of extreme gusts. From theory it follows that the   gust shape resembles the autocorrelation function of turbulence.
2)      Determination of the probability density function of extreme gusts.
3)      Development of a probabilistic method to determine the dynamic response of a wind turbine to extreme gusts.
4)      Implementation of the probabilistic method in a number of existing design packages for wind turbines.
5)      Experimental verification of the predicted loading and response of a wind turbine to extreme gusts.
6)      Synthesis and final reporting.

Results and Exploitation Plans

A probabilistic method has been developed to determine the extreme response of wind turbines to gusts. The method is worked out in such a way that it can be implemented in state-of-the-art design packages for wind turbine design as used by the industry.

The theoretical mean gust shape, as well as the probability of occurrence of gusts, has been verified by measurements. Also a preliminary comparisons with wind turbine load measurements have been carried out. Some more experience, especially parameter studies, as well as experimental verification is needed before the method can be implemented in design standards.
The more accurate description of the extreme loading will enable wind turbine manufacturers to build more reliable and optimised wind turbines.

Contact Information

Wim Bierbooms
tel: +31 (15) 278 2097,
W.A.A.M.Bierbooms(add @tudelft.nl manually)

Partners

Risø National Laboratory (Denmark)
Vestas Wind Systems A/S (Denmark)