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By W. Z. Stepniewski, C. N. Keys
Dover Publications, Inc.Copyright © 1984 Dover Publications, Inc.
All rights reserved.
Volume I of the text entitled Rotary-Wing Aerodynamics is devoted in principle to Basic Theories of Rotor Aerodynamics. However, the exposition of the material is preceded by an introductory chapter wherein the concept of rotary-wing aircraft in general is defined. This is followed by comparisons of the energy effectiveness of helicopters with that of other static-thrust generators in hover; as well as with various air and ground vehicles in forward translation. While the most important aspects of rotor-blade dynamics and rotor control are only briefly reviewed, they should still provide a sufficient understanding and appreciation of the rotor dynamic phenomena related to aerodynamic considerations.
The reader is introduced to the subject of rotary-wing aerodynamics in Ch II by first examining the very simple physicomathematical model of the rotor offered by the momentum theory. Here, it is shown that even this simple conceptual model may prove quite useful in charting basic approaches to helicopter performance predictions; thus providing some guidance to the designer. However, the limitations of the momentum theory; i. e., its inability to account for such phenomena as profile drag and lift characteristics of blade profiles and geometry, necessitated the development of a more sophisticated conceptual rotor model.
The combined biade-eiement and momentum theory presented in Ch III represents a new approach which demonstrates that indeed, greater accuracy in performance predictions is achieved, and this would also become a source of more-detailed guidelines for helicopter design. Even with this improvement, many questions regarding flow fields (both instantaneous and time averaged) around the rotor still remain unanswered.
In the vortex theory discussed in Ch IV, a rotor blade is modeled by means of a vortex filament(s) or vorticity surface; thus opening almost unlimited possibilities for studying the time-average and instantaneous flow fields generated by the rotor. Unfortunately, the price of this increased freedom was computational complexity usually requiring the use of high-capacity computers.
It appears that some of the rotor aerodynamic problems amenable to the treatment of the vortex theory may be attacked with a somewhat reduced computational effort by using the approaches offered by the velocity and acceleration potential theory. This subject is presented in Ch V which also contains a brief outline of the application of potential methods to the determination of flow fields around three-dimensional, nonrotating bodies.
Considerations of airfoil sections suitable for rotors, as presented in Ch VI, completes the sequence on fundamentals of rotary-wing aerodynamics. This material provides a basis for development of the methods for helicopter performance predictions used in Vol II.
In order to create a complete series on Rotary-Wing Aerodynamics the author anticipates a third volume devoted to the application of the basic theories established in Vol I. This volume would include (1) selected problems of helicopter flight mechanics (e.g., ground effect, flight maneuvers, performance limitations, and autorotation); (2) establishment of a link between aerodynamics and design optimization; and (3) development of techniques leading to performance maximization of existing helicopters. In fairness to the aeronautical engineers and designers who have been anxiously awaiting for the publication of this series, the first two volumes are being released prior to the writing of the proposed third volume.
Returning to the present volume, the reader's attention is called to the fact that both SI metric and English unit systems are used in parallel; thus expediting an acquaintance with the metric approach for those who are not yet completely familiar with this subject.
In conclusion, I wish to express my indebtedness to the following persons who generously contributed to this volume: Professor A. Azuma of the University of Tokyo, Japan for his review of the appendix to Ch IV; and to Drs. R. Dat and J.J. Costes of ONERA, France for their valuable inputs and review of Ch V.
W. Z. Stepniewski
Excerpted from Rotary-wing Aerodynamics by W. Z. Stepniewski, C. N. Keys. Copyright © 1984 Dover Publications, Inc.. Excerpted by permission of Dover Publications, Inc..
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