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Delegates are invited to meet and discuss with the poster presenters during the poster presentation sessions between 10:30-11:30 and 16:00-17:00 on Thursday, 19 November 2015.

Lead Session Chair:
Stephan Barth, ForWind - Center for Wind Energy Research, Germany
Philippe Couturier Technical University of Denmark, Denmark
Co-authors:
Philippe Couturier (1) F Steen Krenk (1)
(1) Technical University of Denmark, Kongens Lyngby, Denmark (2) Siemens Wind Power A/S, Brande, Denmark

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2015 and are published here unedited

Philippe Couturier is currently completing a PhD in Mechanical Engineering at the Technical University of Denmark. He has been employed by Siemens Wind Power A/S since 2012. He holds a MASc in Mechanical Engineering from the École Polytechnique de Montréal for which his received the Alexander Graham Bell Canada Graduate Scholarship which is given to high caliber scholars in Canada. He has a bachelor's degree from the University of New Brunswick from which he was awarded the Lieutenant-Governor of New Brunswick Silver Medal as the top student graduating from the faculty of engineering.


Poster

Poster Download poster (8.08 MB)

Abstract

Efficient beam-type structural modeling of rotor blades

Introduction

Wind turbine rotors are becoming increasingly slender with the introduction of larger rotors inviting global beam-type analysis which puts focus on underlying beam theory and general cross-sectional stiffness properties. The blade modeling approach must provide accurate predictions of the blade behavior while being able to easily accommodate geometry and material updates from previous designs.

Approach

As part of a collaborative work between the Technical University of Denmark and Siemens Wind Power A/S, a formulation and analysis procedure of general cross-section properties has been developed. Work has also been done to show how these general properties enter a very efficient equilibrium based beam element.

Main body of abstract

In slender structures, like wind turbine blades, the properties are determined by the mechanical properties associated with the individual beam cross-sections. A formulation for cross-section analysis providing the full six by six stiffness matrix for non-homogeneous and anisotropic sections with coupling between the deformation modes has been developed. This formulation is based on the stress-strain states in the classic six equilibrium modes of a beam by considering a finite thickness slice modeled by a single layer of 3D finite elements. Laminates are modeled using a single element through the wall thickness using layered solid-elements whereby even a complicated cross-section can be modeled with very few elements.
Wind turbine blades exhibit variations in cross-section geometry and material properties along the blade. In the present project a beam element was extended in which the stiffness properties are obtained via flexibility from equilibrium considerations that do not use assumed shape functions. This so called ‘complementary energy’ approach immediately accepts the six by six cross-section stiffness matrices and accounts for geometry and material variations along the blade span.
The beam element has been incorporated into an aeroelastic program at Siemens Wind Power A/S. It has been shown that a blade with complex geometry and material layup can accurately and effectively be modeled using very few elements.

Conclusion

A method of evaluating general cross-sectional properties and beam element stiffness matrices of a rotor blade which accounts for all the possible couplings between the deformation modes and of variations in geometry and material along the blade has been developed. The present methods avoid the need for advanced kinematic analysis of beams and instead hinge on the beam equilibrium modes. Example of an analysis of a Siemens’ rotor blade demonstrates the ease and flexibility in modeling while maintaining accuracy in predicting the blade behavior.


Learning objectives
Audience will become familiar with:
- Cross-sectional analysis requiring limited meshing effort to obtain fully coupled six by six stiffness matrix of cross-sections with complex geometries made of anisotropic materials.
- Equilibrium beam element format immediately accepting six by six stiffness matrices leading to a need for very few elements.
- Example illustrating rotor modeling using novel design tools.