Thinking Fluid Dynamics With Dolphins (Stand Alone)

130 Pages·2002·7.73 MB·English

by  Minoru Nagai

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1. Very high swimming performance of dolphins at successive jumping.
1. Very high swimming performance of dolphins at successive jumping.
2. Standing swimming of a pacific white-sided dolphin. Only the caudal fin supports
all the body weight.
3. Streamline-shaped body of a pacific bottle-nosed dolphin. The vertical flat tail
meets with the horizontal flat caudal fin.
Thinking Fluid Dynamics with Dolphins
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Thinking
Fluid Dynamics
with
Minoru Nagai
Ohmsha Press
Thinking Fluid Dynamics with Dolphins
©2002 Minoru Nagai
All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means, without the prior written permission of the
publisher.
ISBN 4-274-90492-X (Ohmsha)
ISBN 1 58603 231 3 (IOS Press)
Library of Congress Control Number 2001099011
Translated from the original Japanese edition:
"Techno-life Series Iruka ni Manabu Ryutai Rikigaku" published by Ohmsha, Ltd.
©1999 Minoru Nagai
Publisher
Ohmsha, Ltd.
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Chiyoda-ku, Tokyo 101-8460
Japan
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LEGAL NOTICE
The Publisher is not responsible for the use which might be made of the following
information.
Printed in Japan
Preface
This small volume is the English edition of a Japanese book entitled 'Learning fluid
dynamics from dolphins.' The title is derived from the fact that "Dolphins swim too
fast to be explained scientifically." The first person to clearly describe this
phenomenon was the English biologist Sir James Gray (J. Gray, 1936), and this
mystery is known among physicists and specialists in marine engineering as 'Gray's
paradox' or simply as the 'Mystery of dolphins.'
In addition to dolphins, tuna, marlin and some other fish are also famous for
swimming at extraordinary high speeds. Treating both dolphins and fish together in
the same title is difficult because both animals have far different taxonomy -
dolphins belonging to oceanic mammals and tuna and marlin belonging to teleostei
fish. This book uses dolphins as symbolic animals that perform high-speed
swimming. Furthermore, 'dolphins' are chosen as the main character in this English
edition because western readers feel an affinity for them.
This book focuses on young readers, who are interested in technology and science
and who hope to specialize in technological occupations. This book aims to
introduce the developing history of fluid dynamics, and then outlines the research
history and the present recognition of 'Gray's paradox.' Finally, the author's
research, through about three decades, is reviewed. This paradox suggested in the
early 20th century has carried over into the 21st century without finding a complete
solution. It would be a great pleasure for the author if the readers find interest in
fluid dynamics, a discipline that has developed by overcoming numerous paradoxes,
or feel the mood at the forefront of the 'intelligence' of mankind.
The original Japanese edition was published in the autumn of 1999, as a selected
book of 'Techno-life' series by the Japanese Society of Mechanical Engineers.
Fortunately, having the financial support from the Japan Society for the Promotion
of Science, this English edition was realized within three years. Mr. Takayuki
Kawamura, a post MSc researcher at University of the Ryukyus, was in charge of
the language translation from Japanese to English, and Dr. George Yates who is a
friend of the author finally inspected the written English. Dr. Yates was a co-
researcher who was studying animal swimming under Professor T. Y. Wu when the
author temporally stayed at the California Institute of Technology as a visiting
researcher in 1984 - 1985. If this book catches the heart of many readers and is
favored by them, the main contribution is owed to the joint-translators
vi Preface
Mr. Kawamura and Dr. Yates, and the author deeply appreciates their efforts.
Finally, the author dedicates this book to the late Takefumi Ikui, a Professor
Emeritus at Kyusyu University, who was a master of the author, and to my wife,
Megumi Nagai. Teacher Ikui warmly watched the author when the author stepped
into the unknown academic area of 'bio-fluid dynamics,' and cheered up the author.
Megumi has supported the author's irregular researcher life for more than 30 years
since their marriage. None of this book would have appeared without their
existences.
February 2002
Minoru Nagai
Contents
Preface v
Chapter 1 Gray's Paradox
Birth of Gray's Paradox 1
Swimming Speed of Aquatic Animals 2
Observations of Small Fresh-Water Fish - Discovery of the Swimming Number 5
Chapter 2 Early History of Fluid Dynamics - From Aristotle to Newton and
D'Alembert
Aristotle's Paradox 9
Newton's Fluid Dynamics and his Paradox 10
Euler's and Bernoulli's Equations and the Paradox of D'Alembert 14
Lifting Theory 18
Chapter 3 Modern Fluid Dynamics
Navier-Stokes Equations 21
Effects of Small Viscosity 23
Reynolds' Law of Similarity 24
Boundary Layer Theory 26
Laminar Flow and Turbulent Flow 28
Numerical Simulations and Physical Experiments 29
Dynamics of Wings in Real Fluids 32
Chapter 4 Principles of Thrust Generation
Momentum Theory 38
Slender Body Theory 40
Oscillating Wing Theory 43
Chapter 5 Research on High-Speed Swimming Performance
Dimensional Analysis 49
Possibility of Drag Reduction - Flexibility of the Surface Skin 57
Toms Effect 53
Effect of Riblets 57
Studies in Japan 60