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Title:
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TURBU Offshore, Computer Program for Frequency Domain Analysis of Horizontal Axis Offshore Wind Turbines; Implementation
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Author(s):
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Published by:
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Publication date:
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ECN
Wind Energy
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1-9-2004
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ECN report number:
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Document type:
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ECN-C--04-079
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ECN publication
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Number of pages:
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Full text:
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309
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Download PDF
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Abstract:
The design of offshore wind turbines requires to assess a huge amount
of different seastates and wind conditions. Therefor the calculational
efficiency of a combined time/frequency domain approach is attractive.
This was the reason for the development of the frequency domain tool
TURBU Offshore. In addition, such a tool is very feasible for parameter
studies; the dynamics of large offshore wind turbines use to be highly
sensitive to the natural frequency values.
The implementation of TURBU Offshore is based on a modular linear model,
with control loops included. The assumptions for structural and aerodynamic
modelling are state of the art. A multiblade transformation for threebladed
rotors eliminates the rotational coupling between the blades and the
tower. Twobladed rotors require a general handling of this coupling,
which is however enabled by the model setup.The program provides the
mean loads, power spectra and periodic loads, which are merged
to overall load histories for fatigue assessment. Besides, the power
spectra make clear the relevance of poorly damped deformation modes.
Verification exercises point out that TURBU Offshore works well in stationary
conditions and that it predicts damping rates and natural frequencies
properly. It is expected that the use of TURBU Offshore in the design
of wind turbines will yield substantial cost reduction for the nacelle,
rotor and tower.
It is recommended to develop guidelines for the complementary use of
TURBU Offshore with a time domain tool. The derivation of submodels
for control design will be useful, just as the coupling of the linear
structural dynamics model to an advanced aerodynamic code.
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