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Follower force instability of a pod-mounted jet engine

Published online by Cambridge University Press:  04 July 2016

G. T. S. Done
G. T. S. Done*
Affiliation:
Department of Mechanical Engineering, University of Edinburgh
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Extract

In Figs. 1 and 2 are shown two cantilevers, one acted on by a force which maintains its direction as the cantilever deflects, and the other acted on by a follower force which remains tangential to the end of the cantilever. It can be shown, by a simple demonstration, that a follower force is non-conservative (see Bolotin), and therefore has the capability, if it exceeds a certain critical magnitude, of causing oscillatory instability. Thus, the follower force system in Fig. 2 can become unstable in the oscillatory sense while the Euler Strut in Fig. 1, being a conservative system, can become only “statically” unstable, i.e. with the strut diverging monotonically from its equilibrium position. The follower force system can, of course, also become statically unstable. The overall stability of this system has been examined by Bolotin and Beck. Herrmann and Bungay have investigated the stability of a system that combined the main characteristics of the two above in any chosen proportion.

Type
Technical notes
Information
The Aeronautical Journal , Volume 76 , Issue 734 , February 1972 , pp. 103 - 107
Copyright
Copyright © Royal Aeronautical Society 1972 

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References

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