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Critical mach numbers for swept-back wings*

Published online by Cambridge University Press:  07 June 2016

S. Neumark*
Affiliation:
Aerodynamics Department, Royal Aircraft Establishment
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Summary

The effect of yawing a wing in high-speed flow is to delay the onset of shock waves and to increase the critical Mach number. This is because shock waves can only develop along the isobars (running parallel to the edges of the wing, which is assumed untapered and infinitely long), and therefore only the velocity component normal to the edges is significant. To some extent the same is true for a finite sheared or swept-back wing, though the problem is made more complicated by the various additional factors, such as finite aspect ratio (tip effect), plan form (e.g. taper effect) and, what is perhaps the most important, the central kink effect. The experimental technique is extremely cumbersome because of the many shape parameters involved (see Figs. 1, 2, 3), and since analytical solutions present fundamental difficulties and pitfalls, designers tend to favour rule of thumb methods. The present paper contains a general review of the theoretical work done at The Royal Aircraft Establishment, which was limited to the case of zero incidence. This limitation is not a severe one, as flight at high speeds often implies low incidence. Incidences which are not negligible involve the solution of another fundamental problem (that of the lift distribution).

Type
Research Article
Copyright
Copyright © Royal Aeronautical Society. 1950

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Footnotes

*

Paper presented to Section 2, VIIth International Congress of Applied Mechanics, London, September 1948.

References

1. Glauert, H. (1928). The Effect of Compressibility on the Lift of an Aerofoil. Proc. Royal Society A, Vol. 118, 1928.Google Scholar
2. Prandtl, L. (1930). Über Strömungen, deren Geschwindigkeiten mit der Schallgeschwindig-keit vergleichbar sind. Journal of the Aeronautical Research Institute, Tokyo Imperial University, No. 65, 1930.Google Scholar
3. Prandtl, L. (1935). Allgemeine Betrachtungen über die Strömung zusammendrückbarer Flüssigkeiten. Proceedings of the Volta Congress, Rome 1935. Also Zeitschrift für Ange-wandte Mathematik und Mechanik, June 1936.Google Scholar
4. Ludwieg, H. (1940). Pfeilflügeln bei hohen Geschwindigkeiten. Bericht 127 der Lilienthal-Gesellschaft, 1940.Google Scholar
5. Göthert, B. (1940). Berechnung des Geschwindingkeitsfeldes von Pfeilflügeln bei hohen Unterschallgeschwindigkeiten. Bericht 127 der Lilienthal-Gesellschaft, 1940.Google Scholar
6. Göthert, B. (1940). Ebene und raümliche Strömung bei hohen Unterschallgeschwindig-keiten (Erweiterung der Prandtlschen Regel). Bericht 127 der Lilienthal-Gesellschaft, 1940.Google Scholar
7. Ludwieg, H. (1946). Improvement of the Critical Mach Number of Aerofoils by Sweep-back. M.A.P. Völkenrode Report. R. & T. 84. GDC 10/4258 T.Google Scholar
8. Lee, G.H. (1947). Tailless Aircraft Design Problems. Journal of The Royal Aeronautical Society, February 1947, pp. 121 et seq. Google Scholar
9. Richards, E.J. (1948). Practical Design Problems Arising from Sweepback.Anglo-American Aeronautical Conference, London, 3rd-5th September, 1947, Aeronautical Con ference, 1948, pp. 382, 400.Google Scholar