Flutter Model Research Articles

Investigations Concerning the Coupled Wing-Fuselage-Tail Flutter Phenomenon

Results of subsonic model tests and analyses of a critical mode of flutter of a wing-fuselage-horizontal tail combination are presented. Increasing wing sweep can lead to lower flutter speeds. Flutter speeds are a minimum for cantilever wing bending to fuselage torsion frequency ratios in the range of 0.3-0.6. Vertical separation or dihedral angle increases the flutter speed and is more important than longitudinal separation. The aerodynamic interference effect of the wing on the tail is important and a detrimental feature for the configuration used. Flutter analyses using doublet lattice and kernel function unsteady aerodynamics methods were conducted to evaluate the accuracy of the prediction methods and to define controlling criteria. Also, experimental flutter model data and theoretical comparisons in the Mach number range of 0.6 to about 1.0 obtained in investigations conducted for the Air Force Flight Dynamics Laboratory are presented. In general, agreement between predicted and test results for subsonic and transonic investigations is good. Finally, aerodynamic prediction methods are applied to the wing-horizontal tail configuration selected by AGARD for comparisons.

A Comparison of Methods for the Analysis of Wing-Tail Interaction Flutter

Results of an analytical investigation of the aeroelastic stability of variable sweep aircraft, specifically with respect to wing-tail interaction flutter, are presented. Three aerodynamic representations are employed: 1) modified two-dimensional strip theory containing no wingtail aerodynamic interaction, 2) vortex lattice theory containing aerodynamic interaction of wing on tail only, and 3) subsonic kernel function theory containing a complete evaluation of wing-tail aerodynamic interaction. The capability of the interaction methods is established by an application to an experimental flutter model where wing-tail aerodynamic interaction is known to be of importance. The aerodynamic methods are then applied to a particular high performance variable sweep aircraft. The basic flutter mechanisms for this hypothetical aircraft are generated by wing-fuselage mechanical interaction and are predicted by wing aerodynamics alone. Component aerodynamics on wing and tail without interaction do not predict the mechanism. Aerodynamic interaction causes the reappearance of flutter at a velocity 30% lower than generated by the wing alone.

双発機の主翼の振動とフラッタについて

This paper presents the results of the low speed flutter model test and the flutter calculation of a wing with one engine supported by a flexible pylon.These results show the effect of spanwise and chordwise position of engine and, horizontal and vertical stiffness of pylon.The interesting result is that wing flutter mode (symmetry or anti-symmetry) and speed are varied by the value of pylon horizontal stiffness.

A Critical Re-Evaluation of Hydrodynamic Theories and Experiments in Subcavitating Hydrofoil Flutter

A review of relevant hydrodynamic information has been made, with emphasis on the possible cause of serious discrepancies between classical hydrodynamic theory and experiments for subcavitating hydrofoils. The usefulness of the best available wind tunnel and towing tank force measurements is also discussed. It is believed that these data are unreliable, and that the completion of the force calculation based on the classical lifting surface theory and subsequent flutter prediction for an actual flutter model is desirable. Some recommendations for possible future experimental research are also given.

Apparatus for the rapid assessment of high speed flutter model stability

A considerable reduction in the wind tunnel testing time necessary for high speed flutter models can be achieved by the use of a frequency sweep in-phase component response recorder. The damping coefficients and resonant frequencies of a model's significant vibration modes are rapidly assessed from the in-phase response to a harmonic force input as measured by a wattmeter bridge. Satisfactory correlation has been established between wind tunnel results obtained in this way and those from a previously used discrete frequency vector plot apparatus. The latter equipment is still recommended for the more accurate measurements necessary near critical conditions.

Diagnosis of Flutter Model Response Using Time Correlation Techniques

Diagnosis of Flutter Model Response Using Time Correlation Techniques

ボディ・フラッタの近似解析(第1報)

Some rockets or missiles have experienced body flutter. This phenomenon can be treated as a critical motion of the bending vibration combined with the pitching and bouncing of the vehicle. However. the bouncing can be considered to have little effect on the critical speed. The author pro poses here an idealized flutter model to obtain a rough estimation of the effect of the design factors on the critical speed. The model has two massless rigid bars which are connected with a elastic spring at their ends each other and each bar is attached by a concentrated mass at appropriate position. The spring, the masses and their positions are so adjusted that the model and the prototype have equal natural bending frequency, equal total weight and equal moment of inertia. In this report, the center of gravity of the model before the bending deformation is assumed to be fixed on the flight path even during the oscillation to neglect the effect of the bouncing. By such a assumption, the author presents here a simple formuato estimate the critical flutter speed. (See Eq. (17)). The design parameters, which give effect on the flutter, are discussed.

Experimental Model Techniques and Equipment for Flutter Investigations

An outline is given of the uses of flutter models as an aid to the designer in the avoidance of flutter. Details are given of the different types and methods of construction that are used for flutter models and of the various test facilities that are available for high speed and low speed tests. The procedure followed in the U.K. for flutter clearance of the full scale aircraft is described, and the value of the electronic flutter simulator in this field is discussed.

The Design and Testing of Supersonic Flutter Models

The Design and Testing of Supersonic Flutter Models