scholarly journals Geometrical Nonlinear Aeroelastic Stability Analysis of a Composite High-Aspect-Ratio Wing

2008 ◽  
Vol 15 (3-4) ◽  
pp. 325-333 ◽  
Author(s):  
Chang Chuan Xie ◽  
Jia Zhen Leng ◽  
Chao Yang
Keyword(s):  
Stability Analysis ◽  
Aspect Ratio ◽  
Equilibrium State ◽  
High Aspect Ratio ◽  
Unsteady Aerodynamics ◽  
Static Equilibrium ◽  
Beam Model ◽  
Aeroelastic Stability ◽  
Nonlinear Flutter ◽  
Static Equilibrium State

A composite high-aspect-ratio wing of a high-altitude long-endurance (HALE) aircraft was modeled with FEM by MSC/NASTRAN, and the nonlinear static equilibrium state is calculated under design load with follower force effect, but without load redistribution. Assuming the little vibration amplitude of the wing around the static equilibrium state, the system is linearized and the natural frequencies and mode shapes of the deformed structure are obtained. Planar doublet lattice method is used to calculate unsteady aerodynamics in frequency domain ignoring the bending effect of the deflected wing. And then, the aeroelastic stability analysis of the system under a given load condition is successively carried out. Comparing with the linear results, the nonlinear displacement of the wing tip is higher. The results indicate that the critical nonlinear flutter is of the flap/chordwise bending type because of the chordwise bending having quite a large torsion component, with low critical speed and slowly growing damping, which dose not appear in the linear analysis. Furthermore, it is shown that the variation of the nonlinear flutter speed depends on the scale of the load and on the chordwise bending frequency. The research work indicates that, for the very flexible HALE aircraft, the nonlinear aeroelastic stability is very important, and should be considered in the design progress. Using present FEM software as the structure solver (e.g. MSC/NASTRAN), and the unsteady aerodynamic code, the nonlinear aeroelastic stability margin of a complex system other than a simple beam model can be determined.

scholarly journals Aeroelastic Stability Analysis of Damaged High-Aspect-Ratio Composite Wings

2019 ◽  
Vol 56 (5) ◽  
pp. 1794-1808
Author(s):  
Hanif S. Hoseini ◽  
Dewey H. Hodges
Keyword(s):  
Stability Analysis ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Aeroelastic Stability

Aeroelastic Stability Analysis of Aircraft Wings with High Aspect Ratios by Transfer Function Method

2018 ◽  
Vol 18 (12) ◽  
pp. 1850150 ◽  
Author(s):  
Jing Bo Duan ◽  
Zhong Yuan Zhang
Keyword(s):  
Stability Analysis ◽  
Transfer Function ◽  
Aspect Ratio ◽  
Eigenvalue Problem ◽  
High Aspect Ratio ◽  
Function Method ◽  
Complex Eigenvalue ◽  
Governing Equations ◽  
Aeroelastic Stability ◽  
Transfer Function Method

A new method is developed for the aeroelastic stability analysis of a high-aspect-ratio wing based on the transfer function. First, the flutter governing equations for three types of wing elements including clear wing element, wing element with a control surface and that with an external store are, respectively, established by combining the corresponding bend-twist vibration model with the Theodrosen’s unsteady aerodynamic model. Then, in order to use the transfer function method, the element governing equations are processed by the Fourier transform and are formulated in a state-space form using state vector. Based on the finite element procedure, the global governing equations of the whole wing are obtained. Both the flutter velocity and flutter frequency are derived by solving a complex eigenvalue problem with the graphical approach. Additionally, the torsional divergence of the high-aspect-ratio wing is obtained by solving a real eigenvalue problem, which is a degenerated form of the wing flutter governing equations. Finally, illustrative examples are prepared to demonstrate the validity of the present method, which is insensitive to mesh density and does not require structural modal analysis for aeroelastic stability.

scholarly journals Parametric whirl flutter study using different modelling approaches

2021 ◽  
Author(s):  
Christopher Koch
Keyword(s):  
Unsteady Aerodynamics ◽  
Beam Model ◽  
Electric Motors ◽  
Aeroelastic Stability ◽  
Aerodynamic Model ◽  
Lifting Surface ◽  
Aeroelastic Model ◽  
Strip Theory ◽  
Engine Mount ◽  
Whirl Flutter

AbstractThis paper demonstrates the importance of assessing the whirl flutter stability of propeller configurations with a detailed aeroelastic model instead of local pylon models. Especially with the growing use of electric motors for propulsion in air taxis and commuter aircraft whirl flutter becomes an important mode of instability. These configurations often include propeller which are powered by lightweight electric motors and located at remote locations, e.g. the wing tip. This gives rise to an aeroelastic instability called whirl flutter, involving the gyroscopic whirl modes of the engine. The driving parameters for this instability are the dynamics of the mounting structure. Using a generic whirl flutter model of a propeller at the tip of a lifting surface, parameter studies on the flutter stability are carried out. The aeroelastic model consists of a dynamic MSC.Nastran beam model coupled with the unsteady ZAERO ZONA6 aerodynamic model and strip theory for the propeller aerodynamics. The parameter studies focus on the influence of different substructures (ranging from local engine mount stiffness to global aircraft dynamics) on the aeroelastic stability of the propeller. The results show a strong influence of the level of detail of the aeroelastic model on the flutter behaviour. The coupling with the lifting surface is of major importance, as it can stabilise the whirl flutter mode. Including wing unsteady aerodynamics into the analysis can also change the whirl flutter behaviour. This stresses the importance of including whirl flutter in the aeroelastic stability analysis on aircraft level.

Linear and Nonlinear Aeroelastic Analysis of a High Aspect Ratio Wing

2017 ◽  
Author(s):  
F. Bakhtiari-Nejad ◽  
A. H. Modarres ◽  
E. H. Dowell ◽  
H. Shahverdi
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Structural Model ◽  
State Space Model ◽  
Beam Model ◽  
Aeroelastic Analysis ◽  
Structural Nonlinearities ◽  
Flutter Boundary ◽  
Linear And Nonlinear ◽  
Perturbation Equations

In this study, analysis and results of linear and nonlinear aeroelastic of a cantilever beam subjected to the airflow as a model of a high aspect ratio wing are presented. A third-order nonlinear beam model is used as structural model to take into account the effects of geometric structural nonlinearities. In order to model aerodynamic loads, Wagner state-space model has been used. Galerkin method is implemented to solve dynamic perturbation equations about a nonlinear static equilibrium state. The small perturbation flutter boundary is determined by these perturbation equations. The effect of geometric structural nonlinearity of the beam model on the flutter behavior is significant. As it is observed the system’s response to upper speed of flutter goes to limit cycle oscillations and also the oscillations lose periodicity and become chaotic.

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