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Published online by Cambridge University Press: 28 July 2016
The importance of the effects of compressibility on the performance and behaviour of high speed aircraft has been appreciated for a great many years, but in this country it was not until 1937 that serious attention was given to the design of a wind tunnel that would enable the study of compressibility to be undertaken by tests on models of reasonable scale. Prior to 1937 the work which had gone on had established the characteristics of a few aerofoils and simple shapes; at Farnborough the work mainly related to the testing of high tip speed propellers, while at the National Physical Laboratory tests had been made of a two-dimensional character on aerofoils, these tests being made in a small wind tunnel driven on the injector principle, by air discharged from a high pressure reservoir.
Note on page 225 * From elementary theory we have Ho–Po=½ρV2 (l+¼M 2+ …)
Hence V2 = 2 (Ho–Po)/ρ(l+¼M 2+ …)
If a is the velocity of sound in the undisturbed tunnel, a 2=γPo/ρ. Hence M 2 = V 2/a 2 = 2 (Ho–Po)/γPo (l+¼M 2 …)
so that M is simply a function of the pressure ratio (Ho–Po)/Po and so can be expressed (graphically) as a function of (p1–P2)/p2 .
Note on page 234 * High Speed Performance. W. G. A. Perring. Proceedings, Anglo-American Conference, R.Ae.S., London, 1948.
Note on page 245 * Modern Developments for Fluid Dynamics, p. 630.
