Nonlinear Stability Analysis and Experimental Exploration of Limit Cycle Oscillations with Flared Folding Wingtips

Healy, Fintan; Cheung, Ronald C.; Rezgui, Djamel; Cooper, Jonathan E.

doi:10.2514/6.2022-0657

Cited by 6 publications

(7 citation statements)

References 31 publications

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“…Furthermore, as done by Healy et al [18], from the structural point of view, the hinge is considered to have a zero flare angle to simplify the kinematic equations while still accounting for the torsional and bending deformation at the tip of the wing, 𝜂 ℎ and ℎ ℎ , and the total rotation angle of the FFWT, 𝛾, which is a sum of the fold angle, 𝜃, and the slope angle due to bending at the tip node, 𝛽 ℎ . Equation 10 presents the position of the FFWT center of gravity (CG), 𝑟 𝑓 𝑤𝑡 , with respect to the global coordinates system accounting for the kinematic constraints, where 𝑅 𝑛 (𝜇) is a counterclockwise rotation around the corresponding axis, 𝑛.…”

Section: Wingtip: Rigid Body and Torsional Springmentioning

confidence: 87%

“…Although the linear stability analysis on the nonlinear static solution presented in Section II.C.3 can provide a good prediction of the aeroelastic stability of the system, the observations in the experimental work [13] and other references [18] suggest that the nonlinear nature of the system will lead to LCOs.…”

Section: Nonlinear Stability Analysismentioning

confidence: 99%

“…On the one hand, 𝛼 𝑔 represents the geometrical angle of attack defined using the geometrically exact representation of the local angle of attack presented by Healy et al in Equation 20 and Equation 21 [18]. This representation conducts a series of rotations on the global velocity vector, defined by 𝑈 and 𝑈 𝑔 , to account for the root angle of attack, 𝛼 0 , the deflections at the tip of the main wing, 𝛽 ℎ and 𝜂 ℎ , the flare angle of the hinge, Λ, and the fold angle, 𝜃.…”

Section: Wingtip: Adapted Strip Theorymentioning

confidence: 99%

“…On the other hand, an elliptic lift distribution, which is representative of the lift distribution over a finite wing [1], is enforced with the factor, 𝑓 𝑒 . However, given that whether the hinge is free or locked affects the lift distribution, as presented by Healy et al [18], two different distributions are considered. When the hinge is locked, one elliptic lift scaling distribution is applied to the whole wing, including the FFWT, as defined by Equation 26.…”

Section: Aerodynamic Scaling Factorsmentioning

confidence: 99%

See 3 more Smart Citations

Nonlinear Low-Fidelity Numerical Model of the Flared Folding Wingtip

Carrillo

Breuker

Sodja

2023

AIAA SCITECH 2023 Forum

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Section: Wingtip: Rigid Body and Torsional Springmentioning

confidence: 87%

Section: Nonlinear Stability Analysismentioning

confidence: 99%

Section: Wingtip: Adapted Strip Theorymentioning

confidence: 99%

Section: Aerodynamic Scaling Factorsmentioning

confidence: 99%

See 2 more Smart Citations

Nonlinear Low-Fidelity Numerical Model of the Flared Folding Wingtip

Carrillo

Breuker

Sodja

2023

AIAA SCITECH 2023 Forum

View full text Add to dashboard Cite

“…They found that changing the root angle of attack of the model can vary the flutter speed by over 25%. Secondly, Healy et al [52] considered the dynamic behaviour of a wing at velocities beyond the flutter boundary. They showed that after the flutter boundary, a stable limit cycle oscillation predominately bounded by geometric nonlinearities appears.…”

Section: Hinged Wingtipmentioning

confidence: 99%

Numerical and experimental studies of aeroelastic hinged wingtips

Balatti¹

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Aeroelasticity is the science that investigates the mutual interaction between aerody-namic, elastic, and inertia forces and how this affects the static and dynamic structural response. Aeroelastic models can be defined considering different levels of fidelity de-pending on the models’ aim. Gust loads are among the most critical cases an aircraft can encounter, and so mitigating the loads enables the design of a lighter structure, consequently reducing production and fuel consumption costs. Hinged wingtips have shown potential to improve the wing aerodynamic performance while alleviating struc-tural loads. The aim of this work is the numerical and experimental study of aeroelastic wings with hinged wingtips subjected to gusts. Measurements from wind tunnel tests are used to validate the numerical model. Two numerical models, representative of the same aircraft with hinged wingtips subjected to gusts, were considered, a detailed and a simplified one. The latter model, due to its low number of degrees of freedom, was used for wingtip design optimisation. Gust and turbulence events cannot be measured di-rectly, but they can be identified from in-flight measurements. Cubic B-spline functions were used for gust identification considering simulated flight data from the simplified and detailed models. Results have shown the ability of the simplified model to identify the gust and turbulence considering simulated data from the detailed model. To validate the numerical models, a gust generator was designed, installed and commissioned for the Swansea University wind tunnel. Experimental results have shown the difficulty of creating a perfect ‘1-cos’ gust at the desired location. Two techniques to improve the ‘1-cos’ gust were considered. In the first case, the transfer function between the vane rotation and the gust produced at the aircraft model location was identified, and its in-verse was used to calculate the vane rotation. The improvements using this approach are limited by the strong nonlinearity of the aerodynamics. A parametric study of the vane rotation has shown that a more complicated vane rotation function allows ‘1-cos’ gusts at the aircraft model location to be obtained with a mean square error two orders of magnitude smaller than the initial case. An elastic wing able to accommodate different wingtips was manufactured. Three wingtips, namely a fixed wingtip, a hinged wingtip, and a hinged wingtip with a torsional spring at the hinge were considered. Static and dynamic wind tunnel tests have shown the potential of hinged wingtips in reducing wing gust loads. Measured gust loads were used to validate the aeroelastic models.

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