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Research Papers

A New Dynamical Model of Flexible Cracked Wind Turbines for Health Monitoring

[+] Author and Article Information
M. A. Ben Hassena

Research Group on Intelligent Machines,
National Engineering School of Sfax,
University of Sfax,
BP 1173,
3038 Sfax, Tunisia
e-mail: b.hassena.med.amin@gmail.com

F. Najar

Applied Mechanics and Systems
Research Laboratory,
Tunisia Polytechnic School,
University of Carthage,
BP 743,
2078 La Marsa, Tunisia

B. Aydi

Engineering Science and Mechanics,
Virginia Tech,
223 Norris Hall,
Blacksburg, VA 24061

S. Choura

Research Group on Intelligent Machines,
National Engineering School of Sfax,
University of Sfax,
BP 1173,
3038 Sfax, Tunisia

F. H. Ghorbel

Department of Mechanical Engineering
and Materials Science,
Rice University,
6100 Main Street,
Houston, TX 77005-1892

Contributed by the Dynamic Systems Division of ASME for publication in the Journal of Dynamic Systems, Measurement, and Control. Manuscript received July 20, 2011; final manuscript received September 12, 2012; published online March 28, 2013. Assoc. Editor: Nariman Sepehri.

J. Dyn. Sys., Meas., Control 135(3), 031013 (Mar 28, 2013) (12 pages) Paper No: DS-11-1216; doi: 10.1115/1.4023210 History: Received July 20, 2011; Revised September 12, 2012

We develop a mathematical model of a large-scale cracked horizontal axis wind turbine (HAWT) describing the flapping flexure of the flexible tower and blades. The proposed model has enough fidelity to be used in health monitoring applications. The equations of motion account for the effect of the applied aerodynamic forces, modeled using the blade element momentum (BEM) theory, and the location and shape of a crack introduced into one of the blades. We first examine the static response of the HAWT in presence of the crack, and then we formulate the eigenvalue problem and determine the natural frequencies and associated mode shapes. We show that both shape and location of the crack influence the first four natural frequencies. The dynamic response of the HAWT subjected to wind and gravity is obtained using a Galerkin procedure. We conduct a parametric analysis to investigate the influence of the crack on the eigenstructure and overall dynamics. The simulations depict that the first four natural frequencies are reduced as the crack size become more important. We also conclude that the tower root moment may be considered as potential indicators for health monitoring purposes.

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References

Figures

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Fig. 1

(a) Schematic of the HAWT and (b) blades' attached frames

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Fig. 2

Crack position parameters

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Fig. 3

Blade element velocities and angles

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Fig. 4

Curve fitting of the out-of-plane force FXB

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Fig. 5

First set of mode shapes

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Fig. 6

Influence of crack location with small size

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Fig. 7

Influence of crack location with large size

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Fig. 8

Convergence of the tower and first blade solutions using m = 4 and m = 8

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Fig. 9

Response of the cracked HAWT out-of-plane vibration: (solid) without rotation (dashed) with rotation θ·=π2

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Fig. 10

Tip displacement and root moment errors of the HAWT in the presence of crack and rotating hub

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Fig. 11

Influence of the crack width on the tip deflection of the first blade and root moment of the tower

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Fig. 12

Influence of the crack position on the tip deflection of the first blade and root moment of the tower

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Fig. 13

Influence of the crack depth on the tip deflection of the first blade and root moment of the tower

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Fig. 14

Tower root moment approximation

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