Importance of Unsteady Aerodynamics for Space Shuttle Ascent Aeroelastic Stability

1975 ◽  
Vol 12 (3) ◽  
pp. 129-130 ◽  
Author(s):  
J. Peter Reding ◽  
Lars E. Ericsson
Keyword(s):  
Space Shuttle ◽  
Unsteady Aerodynamics ◽  
Aeroelastic Stability

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.

Influence of unsteady aerodynamics on rotor blade aeroelastic stability and response

AIAA Journal ◽  
1990 ◽  
Vol 28 (10) ◽  
pp. 1806-1812 ◽  
Author(s):  
P. P. Friedmann ◽  
L. H. Robinson
Keyword(s):  
Rotor Blade ◽  
Unsteady Aerodynamics ◽  
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.

Periodicity, Superposition, and 3D Effects in Supersonic Compressor Flutter Aerodynamics

1988 ◽  
Author(s):  
G. A. Gerolymos
Keyword(s):  
Euler Equations ◽  
Traveling Wave ◽  
Unsteady Aerodynamics ◽  
Structural Vibration ◽  
Blade Surface ◽  
Aeroelastic Stability ◽  
Amplitude Response ◽  
Supersonic Flutter ◽  
3D Effects ◽  
Annular Cascade

In this work, a family of methods, both blade-to-blade surface and 3D, based on the numerical integration of the unsteady Euler equations, are used in studying various aspects of the unsteady aerodynamics of vibrating compressor cascades, in the supersonic flutter region. Most aerodynamic methods assume a traveling wave assembly mode of structural vibration, and suppose that the associated chorochronical periodicity is also encountered in the flowfield. This hypothesis has been tested by simulating the flow in a full annular cascade and has been verified in all the cases we have studied. When analyzing the aeroelastic stability of cascades, some assembly modal basis must be used. This, especially in presence of mistuning, relies on modal superposition hypotheses and linearity assumptions. The superposition assumption seems to be justified and the linear range of the amplitude-response is fairly large, although it varies greatly with frequency. Finally, an assessment of the importance of unsteady 3D effects is attempted using the 3D method.

Aeroelastic Stability of Space Shuttle Protuberances

1982 ◽  
Vol 19 (4) ◽  
pp. 307-313 ◽  
Author(s):  
L.E. Ericsson ◽  
J.P. Reding
Keyword(s):  
Space Shuttle ◽  
Aeroelastic Stability

scholarly journals Advanced Ducted Engines: Impact of Unsteady Aerodynamics on Fan Vibration Properties

1992 ◽  
Author(s):  
Arno H. Klose
Keyword(s):  
Mode Coupling ◽  
Unsteady Aerodynamics ◽  
Light Weight ◽  
Aeroelastic Stability ◽  
Resonant Frequencies ◽  
Aerodynamic Loads ◽  
Reinforced Plastics ◽  
Unsteady Aerodynamic ◽  
Vibration Properties ◽  
Carbon Fibre Reinforced Plastics

Fans of Advanced Ducted Engines (ADE) will be built from light-weight materials such as carbon-fibre-reinforced plastics (CFRP). Due to their low density, the aeroelastic behaviour of these fan blades is significantly different from that of conventional titanium fan blading. Calculations performed during the design of ADE fan bladings show that self-induced aerodynamic loads can significantly alter the resonant frequencies; furthermore, aerodynamic coupling of the different in-vacuo eigenmodes can occur. This is not the case for conventional titanium fan blading, where the vibration properties are largely unaffected by unsteady aerodynamic forces. It is concluded that for light-weight fan blading, it is necessary to take into account aerodynamic stiffening and aerodynamic mode coupling when computing eigenfrequencies and aeroelastic stability.

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