Real actuator effects and the aerodynamic energy method

1988 ◽  
Vol 92 (912) ◽  
pp. 77-83 ◽  
Author(s):  
A. Simpson
Keyword(s):  
Energy Method ◽  
Normal Vibration ◽  
Control Law ◽  
Vibration Modes ◽  
Aerodynamic Forces ◽  
Flutter Suppression ◽  
Active Controls

Summary The aerodynamic energy method provides a means of flutter-suppression control-law design based wholly on oscillatory aerodynamic forces on a notional structure with notional normal vibration modes. The method has been proposed as a means of flutter suppression regardless of structural considerations, other than those mentioned. As originally conceived, the method is based upon the assumption of totally irreversible active controls. In this paper, the effects of finite impedance of actuators on the implementation of the method are investigated analytically. The conclusions do not augur well for the method.

Correlation of Microwave Dielectric Properties and Normal Vibration Modes of Ba(Mg1/3Ta2/3)O3-Series Materials

2004 ◽  
Vol 13 (1-3) ◽  
pp. 271-275 ◽  
Author(s):  
Yi-Chun Chen ◽  
Hsiu-Fung Cheng ◽  
Chia-Chi Lee ◽  
Chih-Ta Chia ◽  
Hsiang-Lin Liu ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Normal Vibration ◽  
Microwave Dielectric Properties ◽  
Vibration Modes ◽  
Microwave Dielectric

Calculation of the Response of a Fighter Aircraft to Turbulent Air and a Comparison with Flight Measurements

1968 ◽  
Vol 72 (688) ◽  
pp. 303-309 ◽  
Author(s):  
C. G. B. Mitchell
Keyword(s):  
Structural Flexibility ◽  
Vibration Modes ◽  
Frequency Range ◽  
Aerodynamic Forces ◽  
Fighter Aircraft ◽  
Surface Theory ◽  
Short Period ◽  
Rigid Body Modes ◽  
Dutch Roll ◽  
Flight Measurements

Summary:— The response of a P1a fighter aircraft to vertical and lateral harmonic gusts is calculated, and the predicted spectra for response accelerations at many points on the structure compared with previous flight measurements in continuous turbulence. The frequency range for the comparison is 0.45 c/s to 30 c/s and the response includes the short period pitching and the dutch roll rigid–body modes as well as oscillations in five symmetric and four anti–symmetric flexible modes. Structural flexibility is represented by measured vibration modes and aerodynamic forces are calculated by an oscillatory lifting surface theory.

Coupled Blade-Disk-Shroud Flutter Instabilities in Turbojet Engine Rotors

1967 ◽  
Vol 89 (3) ◽  
pp. 419-426 ◽  
Author(s):  
F. O. Carta
Keyword(s):  
Energy Method ◽  
Empirical Data ◽  
Parametric Study ◽  
Vibration Modes ◽  
Coupled Vibration ◽  
Flutter Instability ◽  
Rotating Blade ◽  
Turbojet Engine ◽  
High Incidence ◽  
Engine Rotors

An energy method is used to investigate a flutter instability of turbojet engine rotors which is caused by the interactions between unsteady air loading and the coupled vibration modes of the rotating blade-disk-shroud system. It is shown, analytically, in this parametric study that under certain circumstances the coupling between blade modes permits the transfer of energy from the air to the blade-disk-shroud system, giving rise to a self-excited instability. Both unsteady potential flow theory and empirical data for oscillating airfoils at high incidence are used.

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