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Mixing and the Jet Flap

Published online by Cambridge University Press:  07 June 2016

B. S. Stratford
B. S. Stratford*
Affiliation:
National Gas Turbine Establishment
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Summary

One of the main problems associated with the “ Jet Flap ” concerns the discrepancy in thrust between idealised theory and the experimental results. This discrepancy is attributable to the mixing with the surrounding flow of the thin two-dimensional jet while still in close proximity to the aerofoil. The effect of the mixing may be calculated to a first approximation from a formula derivable from first principles, while certain second order effects, which can be significant, may be considered qualitatively.

It is concluded that.

  • (i) the full thrust should be experienced by a jet flapped aircraft at cruise,

  • (ii) it should be possible to attain a low form drag at cruise in comparison with a conventional aircraft,

  • (iii) at take-off, an aircraft using a shrouded jet flap would have better thrust recovery than one using a pure jet flap (which shows appreciable losses),

  • (iv) the use of by-pass engines would further improve the thrust characteristics,

  • (v) the practical gains from thrust augmentation, as obtained by controlling the mixing, seem likely to be small.

Type
Research Article
Information
Aeronautical Quarterly , Volume 7 , Issue 2 , May 1956 , pp. 85 - 105
Copyright
Copyright © Royal Aeronautical Society. 1955

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References

1. Stratford, B. S. Early Thoughts on the Jet Flap. The Aeronautical Quarterly, February 1956.Google Scholar
2. Davidson, I. M. The Jet Flap. Journal of the Royal Aeronautical Society, January 1956.Google Scholar
3. Dimmock, N. A. An Experimental Introduction to the Jet Flap. Unpublished Report of the National Gas Turbine Establishment, 1955.Google Scholar
4. Dimmock, N. A. Some Further Jet Flap Experiments. Unpublished Memorandum of the National Gas Turbine Establishment, 1956.Google Scholar
5. Stratford, B. S. A Further Discussion on Mixing and the Jet Flap. To be published in The Aeronautical Quarterly.Google Scholar
6. Squire, H. B. and Young, A. D. The Calculation of the Profile Drag of Aerofoils. R. & M. 1838, November 1937.Google Scholar
7. Goldstein, S. (Editor). Modern Developments in Fluid Dynamics. First Edition. Vol. II, Chapter XIII, pp. 592–4. Oxford University Press, 1938.Google Scholar
8. Kuethe, A. M. Investigations of the Turbulent Mixing Regions formed by Jets. Journal of Applied Mechanics, Vol. II, pp. 87–95, 1935.Google Scholar