Focused on the features and requirements of flutter boundary prediction (FBP), the method presented here is introduced and investigated around precision, anti-noise and short sample.

Two standard aeroelastic computing examples(2D Isogai wing with S type flutter boundary and 3D transonic flutter example-AGARD445.6 wing) are computed. The computed flutter boundaries based on ROM are well compared with those of the directly coupling CFD/CSD method.

The panel flutter boundaries are finally determined and the effect of temperature, airflow speed, etc, on the panel flutter characteristics is analyzed.

(4) . The Newmark method is used to solve the panel flutter equations in time domain. The linear flutter boundaries are determined and the effect of temperature on flutter boundaries is analyzed.

The results show that at δ=0.5mm tip clearance due to decrease secondary flows loss the exicted vibration energy of flow is increased, then the scope of blade stall flutter is enlarged and the flutter-boundary is removed forward.

The flutter calculation and experiments are performed for two-dimensional wing with external store, the effects of pylon pitching stiffness on the flutter speed are investigated.

Focused on the nonstationary features and analysis requirements of flutter test data, the application scheme is brought forward for flutter signal processing.

Fixed points of the system are found analytically and regions of limit cycle oscillations are detected for velocities well below the divergent flutter boundary.

Our approach is to use the transversality theorem in locating such flutter boundaries using this criterion:at a flutter boundary, the characteristic polynomial does not intersect the axis of the abscissa transversally.

AF is linearly interpolated with Dynamic pressure to obtain Flutter boundary.

Accurate prediction of flutter boundary prior to and during flight testing is critical for expanding an aircraft's flight envelope.

A flutter point obtained in the wind-tunnel test is com pared with a flutter boundary calculated from an analysis based on a Donnell-type theory.

As a check on the current energy methods, the stall flutter boundaries for two real rotors are predicted by using the present method and the results are compared with the experiments and those predicted by using an energy method.

A new method of calculating the flutter boundaries of undamped aeroelastic "typical section" models is presented.

Our approach is to use the transversality theorem in locating such flutter boundaries using this criterion:at a flutter boundary, the characteristic polynomial does not intersect the axis of the abscissa transversally.

Formulas for computing the flutter boundaries of structures with two degrees of freedom are presented, and extension to multi degree of freedom systems is indicated.

Figure 11showsthe predicted symmetric and antisymmeaic flutter boundaries for this configurationwith respect to Mach number.

The coupled flap-lag flutter stability of a helicopter rotor blade in hover is investigated by using a finite element formulation based on the principle of minimum potential energy. Quasisteady two-dimensional airfoil theory is used to obtain the aerodynamic loads. The resulting nonlinear equations of motion are solved for steady state blade deflections. The flutter solution is calculated on the assumption that the blade motion is a small perturbation about the steady solution. Finally, results are presented...

The coupled flap-lag flutter stability of a helicopter rotor blade in hover is investigated by using a finite element formulation based on the principle of minimum potential energy. Quasisteady two-dimensional airfoil theory is used to obtain the aerodynamic loads. The resulting nonlinear equations of motion are solved for steady state blade deflections. The flutter solution is calculated on the assumption that the blade motion is a small perturbation about the steady solution. Finally, results are presented for hingeless rotor blade configurations.

Some improvements in previous computation models of blade stall flutter in axial-flow compressors have been made on both aerodynamics and structural dynamics so as to make the models more practical.The calculations show that the effect of in-passage shock and separation flow on the aeroelastic stability of a blading system vibrating in a pure bending mode with single degree of freedom is qualitatively different from that in a predominant bending mode with two degrees of freedom.The coupling of bending and torsion...

Some improvements in previous computation models of blade stall flutter in axial-flow compressors have been made on both aerodynamics and structural dynamics so as to make the models more practical.The calculations show that the effect of in-passage shock and separation flow on the aeroelastic stability of a blading system vibrating in a pure bending mode with single degree of freedom is qualitatively different from that in a predominant bending mode with two degrees of freedom.The coupling of bending and torsion degrees of freedom is probably one of the most important factors which cause onset of the stall flutter .Finally, the stall flutter boundary is preliminarily predicted for an actual rotor and the results are compared with the corresponding experimental data.

Blade flutter is a challenging problem in the development of modern aerocraft engines of high thrust-weight ratio. The blade stall flutter is more common and serious than other kinds of flutter, which, resulted from aeroelastic instability in varieties of turbomachinery. Because of the complication of the problem, the study on the prediction of the flutter is still in its early stage.Some improvements have been made in this paper to develop a prediction method which can reflect the interaction between the aerodynamic...

Blade flutter is a challenging problem in the development of modern aerocraft engines of high thrust-weight ratio. The blade stall flutter is more common and serious than other kinds of flutter, which, resulted from aeroelastic instability in varieties of turbomachinery. Because of the complication of the problem, the study on the prediction of the flutter is still in its early stage.Some improvements have been made in this paper to develop a prediction method which can reflect the interaction between the aerodynamic and structural factors of the problem.On the basis of a vibration model in two degrees of freedom, which was developed in the case of incompressible or pure supersonic flow around a flat cascade, some systematic coupling terms of structural dynamics are introduced in form of exciting forces according to the characteristics of real rotors. The systematic structural coupling coefficients are determined by solving the vibration equations inversely, which reflected the out-of-phase vibration of bending and torsion due to the existence of travelling wave.The improved model of structural dynamics is combined with the unsteady aerodynamic model incorporating the effect of transonic separation flow around a cascade to simulate the aeroelastic system of blade stall flutter, which is solved in an iteration way.It is shown, by two examples for real rotors, that the predictions by the present method agree well with the experiments. The computation results doesn't show much difference with those by an energy method developed by the authors previously. This means that the application of the energy methods to the study of the blade stall flutter is still acceptable. However, the present method can incorporate the response of structural dynamics of the problem and reflect the interaction between the aerodynamic and structural sides in an iterative way. Therefore, as the research on the problem goes en a.nd the required accuracy of the computation is raised further, this kind of methods will be used more and more.