Air-Screws: An Introduction to the Aerofoil Theory of Screw Propulsion (Classic Reprint)

Excerpt from Air-Screws: An Introduction to the Aerofoil Theory of Screw Propulsion

The problem of determining the form of air flow generated by an aerofoil, moving through still air, is one that has so far defied mathematical analysis. This problem, which applies equally to water and other fluids, is one for which a solution has only been obtained when the aerofoil is a flat plate of infinite span) The analytical results however do not conform with those obtained by experiment, and it would seem that the still more complex problem of the curved surface is 'beyond the reach of present-day analysis.

The mathematical theory makes the pressure on a flat surface vary as the 'square of the general velocity of the stream, and experiment has shown that between fairly large limits in velocity this holds good.

Briefly, if an aerofoil be exposed to a moving current of air or, what is the same thing, if an aeroplane wing be moving through still air, the resultant air pressure on the aerofoil may be expressed by the formula (r where (s) denotes the area of the aerofoil surface, and (v) the velocity of flight of the aerofoil relative to the air. (it) is a constant the numerical value of which depends upon the units employed in the measurements of the quantities (r), (s), and (v).

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This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.

Excerpt from Air-Screws: An Introduction to the Aerofoil Theory of Screw Propulsion

With the coming of the Aeroplane the quantitative study of screws working in air has assumed a great importance.

Formerly in the design of screw propellers for marine work experiments with models were carried out and the performance of the full size screw calculated from them, and it was not until 1882 that Drzewiecki first drew attention to a possible more powerful method of design obtained by considering each element along the blade as independent and behaving in the same manner as if moving through the fluid in a straight line.

This method has since assumed great importance in the practical design of air-screw blades, and the results obtained seemed to justify the utilization of this theory as at least approximately correct provided certain limits are not exceeded.

In the present work the theory has been assumed to be absolutely correct, and the results obtained have been carried to their logical conclusions. This has been done for various reasons.

It does not make for completeness in any argument if the results of the initial hypothesis are not carried to their ultimate logical conclusions, and although in the present instance the results so obtained may not be completely borne out in practice, yet, in giving an insight into the applications of the theory, and in establishing at any rate an approximate method for dealing with the many cases arising out of the performances of aircraft, the conclusions arrived at will, it is hoped, not be without interest.

About the Publisher

Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com

This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.