Aeroelasticity of Axially Loaded Aerodynamic Structures for Truss-Braced Wing Aircraft

Nguyen, Nhan T.; Ting, Eric B.; Lebofsky, Sonia

doi:10.2514/6.2015-1840

Cited by 9 publications

(6 citation statements)

References 6 publications

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“…Additionally, it can be seen that the natural frequencies of the torsional and in-plane modes increase, whereas the out-of-plane modes decrease. The trend of increasing natural frequencies with increasing static deformation has been observed in fixed-wing aircraft [25]. However, this trend was observed for all modes of interest.…”

Section: Fig 6 Change In the Natural Frequencies With Increasing Stamentioning

confidence: 79%

Aeroelastic eigenvalue analysis of a variable speed rotor blade with an applied compressive load

Dibble¹,

Ondra

Woods

et al. 2019

AIAA Scitech 2019 Forum

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Variable speed rotors are one possible way to meet the industry's increasing demands on noise emissions, flight envelopes and power requirements. The use of this technology is largely prohibited due to the presence of dynamic interactions at various rotor speeds that would lead to excessive vibratory loads. One concept being considered to overcome this is modal tuning by means of an applied compressive load. Herein, the impact of the combined effects of compressive loading, aerodynamic loading in hover and reduced rotor speeds on rotor blade's aeroelastic properties are investigated. A structurally nonlinear blade model directly coupled with an unsteady aerodynamic blade element model is formulated and verified. The model is used to show that moderate static deformations due to aerodynamic loads can introduce stiffening as well as softening effects. Compressive loading is then applied and it is shown that even at large compressive loads the blade's internal tension remains dominated by centrifugal loading. Finally, a study of the change in natural frequencies and damping ratios at various rotor speeds and compressive loadings is performed. It shows that natural frequencies and damping ratios are both affected by changing rotor speed and compressive load and that the sensitivity to the compressive load is greatest at lower rotor speeds.

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Section: Fig 6 Change In the Natural Frequencies With Increasing Stamentioning

confidence: 79%

Aeroelastic eigenvalue analysis of a variable speed rotor blade with an applied compressive load

Dibble¹,

Ondra

Woods

et al. 2019

AIAA Scitech 2019 Forum

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show abstract

“…This tension-induced stiffening effect is a geometric nonlinearity which should be captured in aeroelastic analyses of the TTBW configuration. 11 Thus, the TTBW structure is inherently a nonlinear structure. A recent study has investigated the effect of axial loading of the TTBW configuration on the flutter speed.…”

Section: Figure 1 Boeing Sugar Transonic Truss-braced Wing (Ttbw) Aircraft Conceptmentioning

confidence: 99%

Aero-Structural Modeling of the Truss-Braced Wing Aircraft Using Potential Method with Correction Methods for Transonic Viscous Flow and Wing-Strut Interference Aerodynamics

Fugate

Nguyen

Xiong

2019

AIAA Aviation 2019 Forum

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This paper describes an aero-structural modeling method for the Transonic Truss-Braced Wing (TTBW) aircraft using VSPAERO. A vortex-lattice model of the TTBW aircraft is developed, and a transonic and viscous flow correction method is implemented in the VSPAERO models to account for transonic and viscous flow effects. A correction method for the wing-strut interference aerodynamics is developed and applied to the VSPAERO solver. Also, a structural dynamic finite-element model of the TTBW aircraft is developed. This finite-element model includes the geometric nonlinear effect due to the tension in the struts which cause a deflectiondependent nonlinear stiffness. The VSPAERO models are coupled to the finite-element model to provide a rapid capability for aero-structural modeling and flutter analysis. A flight-optimized jig twist model is being developed and will be applied for the purpose of generating a full flight dynamic model of the TTBW aircraft.

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“…Thus, the difference in the bending deflection between the linear and nonlinear bending theories is due to mostly the aeroelastic term in the left hand side which contributes positively to the wing stiffness. For sweptback wings, truss-braced wings, 18 and rotary wings, the effect of the axial tension P x can be a dominant factor. Then, the significance of the nonlinear bending deflection can be much more pronounced.…”

Section: B Examplementioning

confidence: 99%

Large Deflection Aeroelasticity and Aeroelastic Lifting Line Theory for Examination of Aerodynamic Effects and Nonlinear Limit Cycle Oscillations

Nguyen

Ting

2018

2018 AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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This paper investigates the effects of nonlinear large deflection bending on the aerodynamic performance and aeroelasticity of a high aspect ratio flexible wing. A nonlinear large deflection theory is developed for aeroelasticity to account for large deflection bending. An analysis is conducted to compare the nonlinear bending theory with the linear bending theory. The results show that the nonlinear bending theory is length-preserving whereas the linear bending theory causes a non-physical effect of lengthening of the wing structure under the no axial load condition. A modified lifting line theory is developed to compute the lift and drag coefficients of a wing structure undergoing a large bending deflection. The lift and and drag coefficients are more accurately estimated by the nonlinear bending theory due to its length-preserving property. The nonlinear bending theory yields a lower lift and higher induced drag than the linear bending theory. The nonlinear large deflection bending also can affect the structural dynamics of a high aspect ratio wing significantly. Limit cycle oscillations are a nonlinear phenomenon which arises from geometric nonlinearity and other sources of nonlinearities. Large deflection can manifest itself in limit cycle oscillations whereby linear flutter behaviors can result in an increase in the bending deflection up to a point where the geometric nonlinearity due to the large deflection begins to set in that results in limit cycle oscillations.

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Aeroelasticity of Axially Loaded Aerodynamic Structures for Truss-Braced Wing Aircraft

Cited by 9 publications

References 6 publications

Aeroelastic eigenvalue analysis of a variable speed rotor blade with an applied compressive load

Aeroelastic eigenvalue analysis of a variable speed rotor blade with an applied compressive load

Aero-Structural Modeling of the Truss-Braced Wing Aircraft Using Potential Method with Correction Methods for Transonic Viscous Flow and Wing-Strut Interference Aerodynamics

Large Deflection Aeroelasticity and Aeroelastic Lifting Line Theory for Examination of Aerodynamic Effects and Nonlinear Limit Cycle Oscillations

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