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Research Papers

Experimental and Numerical Investigations on Nonlinear Aeroelasticity of Forward-Swept, Compliant Wings

[+] Author and Article Information
Ghalib Y. Thwapiah

 Swiss Federal Laboratories for Materials Testing and Research (Empa), Überlandstrasse 129, CH 8600 Dübendorf, Switzerlandghalub@yahoo.com

L. Flavio Campanile1

 Swiss Federal Laboratories for Materials Testing and Research (Empa), Überlandstrasse 129, CH 8600 Dübendorf, Switzerlandflavio.campanile@empa.ch

1

Corresponding author.

J. Mech. Des 134(1), 011009 (Jan 05, 2012) (9 pages) doi:10.1115/1.4005441 History: Received October 10, 2010; Revised October 25, 2011; Published January 05, 2012; Online January 05, 2012

At the beginning of aviation history, aeroelastic static instabilities represented a problem in operating monoplane aircraft. After being discovered, they were systematically avoided, since they would have led to large deformations and structural failure. A new idea (active aeroelasticity) reverts this approach and utilizes static instabilities to realize wing morphing instead of avoiding them. Another innovative idea (compliant systems) deals with structures designed to achieve large deformations within the elastic range of the material. Joining those two ideas leads to a novel class of airfoil structures (active aeroelastic, compliant airfoils) which enable operation at and beyond aeroelastic instabilities. Such structures need a new modeling approach, which includes nonlinearities of structural and aerodynamic kinds. In this paper, a non linear analysis of aeroelastic bending divergence (a phenomenon which concerns forward-swept wings) is presented, initially based on so-called low-fidelity models. Such models are, to some extent, inaccurate but allow a good insight into the physical behavior of the phenomenon and are very useful in preliminary design. The results of wind-tunnel tests follow, which were performed to investigate the aeroelastic response of a compliant airfoil model near divergence. Finally, high fidelity simulation results based on state-of-the-art methods (finite element method and fluid-structure-interaction) are shown and discussed. Those tools allow the prediction of the system response more accurately and are therefore well suited to the detailed design of active aeroelastic, compliant airfoils.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Stability analysis results of swept lifting airfoil. Adapted from Ref. [6].

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Figure 2

Coordinate systems for the airfoil

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Figure 3

Cross section of the compliant airfoil model

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Figure 4

Instability diagrams (experimental and from low-fidelity analysis) for different values of the angle of incidence

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Figure 5

Lift force (experimental)

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Figure 6

Lift coefficient (experimental and from low-fidelity analysis)

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Figure 7

Root moment (experimental)

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Figure 8

Root moment coefficient (experimental)

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Figure 9

Drag coefficient (experimental)

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Figure 10

Lift-to-drag ratio (experimental)

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Figure 11

Fluid mesh of the FSI calculations

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Figure 12

Structural model for the FSI calculations

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Figure 13

Lift force (experimental and from FSI simulation)

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Figure 14

Drag force (experimental and from FSI simulation)

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Figure 15

Bending curves of the shear centre line of the airfoil (from circle-arc and FEM analysis)

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