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ECN publication
Enhanced approach for simulation of rotor aerodynamic loads
Published by: Publication date:
ECN Wind Energy 6-2-2012
ECN report number: Document type:
ECN-M--12-003 Conference Paper
Number of pages: Full text:
17 Download PDF  

Uncertainty in aerodynamic load prediction is an important parameter driving the price of wind energy, especially for offshore locations. Blade Element Momentum (BEM) theory is the current standard for estimating the wind forces in load case calculations. The variety between the several engineering extensions used in different BEM implementations is huge. In addition to that, the assumption of radial independence of the annuli and the lack of wake modelling are well known shortcomings of this method. A more detailed approach to model the rotor aerodynamics is presented by a vortex line method with a free vortex wake. Contrary to the BEM method, it is possible to accurately simulate innovative rotor geometries exhibiting distributed control or non-straight blades.

A survey is made to investigate the influence of the various modelling options for several operating conditions. Firstly a rigid turbine is subject of investigation by means of a comparison to the NASA-AMES and MEXICO wind tunnel test databases. The predictive capability of the BEM modelling falls short for yawed flow and dynamic inflow cases. Coupling the aerodynamic solver to a structural dynamics code allows for a full aero-elastic wind turbine simulation in the time domain. The results are in agreement with measurements of a turbine at the ECN test site Wieringermeer. In addition to that the influence of the various modelling options on the aerodynamic damping is investigated. The research sheds new light on the uncertainties and capabilities of rotor aerodynamics modelling for design calculations. The long term benefit lies in improved guidelines for wind turbine design, thereby reducing the cost of offshore wind energy.

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