FLUID-STRUCTURE INTERACTIONS SLENDER STRUCTURES AND AXIAL FLOW

FLUID-STRUCTURE INTERACTIONS SLENDER STRUCTURES AND AXIAL FLOW.;

A word about la raison d’2tre of this book could be useful, especially since the first question to arise in the prospective reader’s mind might be: why another book on powinduced vibration?

Flow-induced vibrations have been with us since time immemorial, certainly in nature, but also in artefacts; an example of the latter is the Aeolian harp, which also makes the point that these vibrations are not always a nuisance. However, in most instances they are annoying or damaging to equipment and personnel and hence dangerous, e.g. leading to the collapse of tall chimneys and bridges, the destruction of heat-exchanger and nuclear-reactor intemals, pulmonary insufficiency, or the severing of offshore risers. In virtually all such cases, the problem is ‘solved’, and the repaired system remains troublefree thereafter – albeit, sometimes, only after a first and even a second iteration of the redesigned and supposedly ‘cured’ system failed also. This gives a hint of the reasons why a book emphasizing (i) thefundamentals and (ii) the mechanisnis givitig rise to thepowinduced vibration might be useful to researchers, designers, operators and, in the broadest sense of the word, students of systems involving fluid-structure interactions. For, in many cases, the aforementioned problems were ‘solved’ without truly understanding either the cause of the original problem or the reasons why the cure worked, or both. Some of the time-worn battery of ‘cures’, e.g. making the structure stiffer via stiffeners or additional supports, usually work, but often essentially ‘sweep the problem under thc carpet’, for it to re-emerge under different operating conditions or in a different part of the parameter space; moreover, as we shall see in this book, for a limited class of systems, such measures may actually be counterproductive.

Another answer to the original question ‘Why yet another book?’ lies in the choice of the material and the style of its presentation. Although the discussion and citation of work in the area is as complete as practicable, the style is not encyclopaedic; it is sparse, aiming to convey the main ideas in a physical and comprehensible manner, and in a way that isfun to read. Thus, the objectives of the book are (i) to convey an understanding of the undoubtedly fascinating (even for the layman) phenomena discussed, (ii) to give a complete bibliography of all important work in the field, and (iii) to provide some tools which the reader can use to solve other similar problems.

A second possible question worth discussing is ‘Why the relatively narrow focus?’ By glancing through the contents, it is immediately obvious that the book deals with axial-flow-related problems, while vortex-induced motions of bluff bodies, fluidelastic instability of cylinder arrays in cross-flow, ovalling oscillations of chimneys, indeed all cross-flow-related topics, are excluded. Reasons for this are that (i) some of these topics are already well covered in other books and review articles; (ii) in at least some cases, the fundamentals are still under development, the mechanisms involved being incompletely understood; (iii) the cross-flow literature is so vast, that any attempt to cover it, as well as axial-flow problems, would by necessity squeeze the latter into one chapter or two, at most.

After extensive consultations with colleagues around the world, it became clear that there

was a great need for a monograph dealing exclusively with axial-flow-induced vibrations and instabilities. This specialization translates also into a more cohesive treatment of the material to be covered. The combination of axial flow and slender structures implies, in many cases, the absence or, at most, limited presence of separated flows. This renders analytical modelling and interpretation of experimental observation far easier than in systems involving bluff bodies and cross-flow; it permits a better understanding of the physics and makes a more elegant presentation of the material possible. Furthermore, because the understanding of the basics in this area is now well-founded, this book should remain useful for some time to come.

In a real sense, this book is an anthology of much of the author’s research endeavours over the past 35 years, at the University of Cambridge, Atomic Energy of Canada in Chalk River and, mainly, McGill University – with a brief but important interlude at Cornell University. Inevitably and appropriately, however, vastly more than the author’s own work is drawn upon.

The book has been written for engineers and applied mechanicians; the physical systems discussed and the manner in which they are treated may also be of interest to applied mathematicians. It should appeal especially to researchers, but it has been written for practising professionals (e.g. designers and operators) and researchers alike. The material presented should be easily comprehensible to those with some graduate-level understanding of dynamics and fluid mechanics. Nevertheless, a real attempt has been made to meet the needs of those with a Bachelor’s-level background. In this regard, mathematics is treated as a useful tool, but not as an end in itself.

This book is not an undergraduate text, although it could be one for a graduate-level course. However, it is not written in rext-book format, but rather in a style to be enjoyed by a wider readership.

I should like to express my gratitude to my colleagues, Professor. B.G. Newman for his help with Section 2.2.1, Professors S.J. Price and A.K. Misra for their input mainly on Chapters 3 and 6, respectively, Dr H. Alighanbari for input on several chapters and Appendix F, and Professor D.R. Axelrad for his help in translating difficult papers in Gernian.

I am especially grateful and deeply indebted to Dr Christian Semler for some special calculations, many suggestions and long discussions, for checking and rechecking every part of the book, and particularly for his contributions to Chapter 5 and for Appendix F, of which he is the main creator. Also, many thanks go to Bill Mark for his willing help with some superb computer graphics and for input on Appendix D, and to David Sumner for help with an experiment for Section 4.3.

I am also grateful to many colleagues outside McGill for their help: Drs D.J. Maul1 and A. Dowling of Cambridge, J.M.T. Thompson of University College London, S.S. Chen of Argonne, E.H. Dowel1 of Duke, C.D. Mote Jr of Berkeley, F.C. Moon of Cornell, J.P. Cusumano of Penn State, A.K. Bajaj of Purdue, N.S. Namachchivaya of the University of Illinois, S. Hayama and S. Kaneko of the University of Tokyo, Y. Sugiyama of Osaka Prefecture, M. Yoshizawa of Keio, the late Y. Nakamura of Kyushu and many others, too numerous to name.

My gratitude to my secretary, Mary Fiorilli, is unbounded, for without her virtuosity and dedication this book would not have materialized Finally, the loving support and con stant encouragement by my wife Vrissei’s (Bpiaqi’s) has been a sine qua non for the completion of this book, as my mother’s exhortations to ‘be laconic’ has been useful. For what little versatility in the use of English this volume may display, I owe a great deal to my late first wife, Daisy.

Acknowledgements are also due to the Natural Sciences and Engineering Research Council of Canada, FCAR of QuCbec and McGill University for their support, the Department of Mechanical Engineering for their forbearance, and to Academic Press for their help and  encouragement.

 

Michael P. Paldoussis

McGill Universify,

Montreal, Que‘bec, Canada.

 

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