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An Exploratory Investigation of Some Types of Aeroelastic Instability of Open and Closed Bodies of Revolution Mounted on Slender StrutsAeroelastic instability phenomena of isolated open and closed rigid bodies of revolution free to move under elastic restraint have been investigated experimentally at low speeds by means of models suspended at zero angles of attack and yaw on slender flexible struts from a wind tunnel ceiling. Three types of instability were observed - flutter similar to classical bending-torsion flutter, divergence, and an uncoupled oscillatory instability which consists in nonviolent continuous or intermittent small-amplitude oscillations involving only angular deformations. The speeds at which this oscillatory instability starts were found to be as low as about one-third of the speed at flutter or divergence and to depend on the shape of the body, particularly that of the afterbody, and on the relative location of the elastic axis. An attempt has been made to calculate the airspeeds and, in the case of the oscillatory phenomena, the frequencies at which these instabilities occur by using slender-body theory for the aerodynamic forces on the bodies and neglecting the aerodynamic forces on the struts. However, the agreement between the speeds and frequencies calculated in this manner and those actually observed has been found to be generally unsatisfactory; with the exception of the frequencies of the uncoupled oscillations which could be predicted with fair accuracy. The nature of the observed phenomena and of the forces on bodies of revolution suggests that a significant improvement in the accuracy of analytical predictions of these aeroelastic instabilities can be had only by taking into account the effects of boundary-layer separation on the aerodynamic forces.
Document ID
20090014039
Acquisition Source
Legacy CDMS
Document Type
Other - NACA Research Memorandum
Authors
Clevenson, S. A. (National Advisory Committee for Aeronautics. Langley Aeronautical Lab. Langley Field, VA, United States)
Wildmayer, E., Jr. (National Advisory Committee for Aeronautics. Langley Aeronautical Lab. Langley Field, VA, United States)
Diederich, Franklin W. (National Advisory Committee for Aeronautics. Langley Aeronautical Lab. Langley Field, VA, United States)
Date Acquired
August 24, 2013
Publication Date
June 30, 1953
Subject Category
Aerodynamics
Report/Patent Number
NACA-RM-L53E07
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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