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Published online by Cambridge University Press: 28 July 2016
France, paralysed during many years of a cruel occupation, has been unable to maintain a sustained technical effort, comparable with that of England.
Nevertheless, the work of French engineers was never discontinued. In difficult and sometimes dramatic circumstances, more often than not with only restricted facilities, their work of research continued, stubbornly and in silence.
Note on page No 491 * The pitch angle of a propeller normally refers to the angle between the zero lift axis of a given section and the plane of rotation. The section normally chosen is at 70 per cent, of the blade radius, which is taken from the axis of rotation.
Note on page No 492 * For conversion one metre = 3.281 ft. one Km.p.h. = 0.6214 m.p.h.
Note on page No 499 * For conversion one sq. m. = 10.76 sq. ft.
Note on page No 510 * The Pitot traverse method:— A test method known as the “Pitot traverse method,” consists in measuring the drag of a body by determining the loss of momentum of the air current influenced by the said body.
A steady flow is assumed.
The quantities measured are: the total pressure and the static pressure in a plane downstream of the profile perpendicular to the general current and also the static and total pressures far upstream of the body. The method was established by Betz for incompressible flows and the use of the results was notably simplified by Melvill B. Jones.
The CD value is given by the expression
In practice, only the wake is affected by the integration.
go = upstream infinity total pressure.
Po = upstream infinity static pressure.
g = total pressure in wake.
p = static pressure in wake.
y= transversal distance to an axis parallel with speed.
l = aerofoil chord.
It should be noted that this formula is applicable to profiles where the flow is incompressible.
With a few modifications, it can be extended to compressible flows and bodies of any form.
Note on page No 523 * For conversion, one kilo=2.205 lb.