Page 14 - Fluid-Structure Interactions Slender Structure and Axial Flow (Volume 1)

Preface

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 pow-
induced 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 trouble-
free 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 thepow-
induced 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.

xi