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A note on the propulsive systems of fishes and birds, with possible application to manpowered flight

Published online by Cambridge University Press:  04 July 2016

J. S. Elliott
J. S. Elliott*
Affiliation:
Aerodynamics Department, RAE, Farnborough
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Extract

It has long been pointed out by Gray that large aquatic animals, notably the dolphin, have been observed to achieve speeds which appear to be far beyond their muscular capabilities, unless they somehow experience laminar flow. Many workers have puzzled over this problem, and various possibilities have been propounded. In particular Wu has carried out a long theoretical analysis of the swimming of a slender fish in two dimensions, and he mentions the prospect of the zero momentum wake.

The principle of the zero momentum wake (or boundary layer propulsion, as it is sometimes called) has often attracted the attention of aircraft propulsion engineers. A small wind tunnel experiment by Göbel and Oehler is of interest. They took a circular sieve, representing profile drag, and set this in relation to a propeller of the same diameter as the sieve. The sieve and the propeller were set side-by-side on a bar, and the power required to propel the model was measured. Then the sieve and the propeller were set in tandem, with the sieve in front of the propeller, and the power required measured again. The power required for the tandem arrangement was found to be significantly less than that required for the side-by-side arrangement.

Type
Research Article
Information
The Aeronautical Journal , Volume 88 , Issue 877 , February 2001 , pp. 296 - 298
Copyright
Copyright © Royal Aeronautical Society 1984 

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References

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