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This self-contained book provides an introduction to the
flow-oscillator modeling of vortex-induced bluff-body oscillations.
One of the great challenges in engineering science also happens to
be one of engineering design - the modeling, analysis and design of
vibrating structures driven by fluid motion. The literature on
fluid-structure interaction is vast, and it can be said to comprise
a large fraction of all papers published in the mechanical
sciences. This book focuses on the vortex-induced oscillations of
an immersed body, since, although the importance of the subject has
long been known, it is only during the past fifty years that there
have been concerted efforts to analytically model the general
behavior of the coupling between vortex shedding and structural
oscillations. At the same time, experimentalists have been
gathering data on such interactions in order to help define the
various regimes of behavior. This data is critical to our
understanding and to those who develop analytical models, as can be
seen in this book. The fundamental bases for the modeling developed
in this book are the variational principles of analytical dynamics,
in particular Hamilton's principle and Jourdain's principle,
considered great intellectual achievements on par with Newton's
laws of motion. Variational principles have been applied in
numerous disciplines, including dynamics, optics and quantum
mechanics. Here, we apply variational principles to the development
of a framework for the modeling of flow-oscillator models of
vortex-induced oscillations.
The purpose of this monograph is to show how a compliant offshore
structure in an ocean environment can be modeled in two and three
di mensions. The monograph is divided into five parts. Chapter 1
provides the engineering motivation for this work, that is,
offshore structures. These are very complex structures used for a
variety of applications. It is possible to use beam models to
initially study their dynamics. Chapter 2 is a review of
variational methods, and thus includes the topics: princi ple of
virtual work, D'Alembert's principle, Lagrange's equation, Hamil
ton's principle, and the extended Hamilton's principle. These
methods are used to derive the equations of motion throughout this
monograph. Chapter 3 is a review of existing transverse beam
models. They are the Euler-Bernoulli, Rayleigh, shear and
Timoshenko models. The equa tions of motion are derived and solved
analytically using the extended Hamilton's principle, as outlined
in Chapter 2. For engineering purposes, the natural frequencies of
the beam models are presented graphically as functions of
normalized wave number and geometrical and physical pa rameters.
Beam models are useful as representations of complex struc tures.
In Chapter 4, a fluid force that is representative of those that
act on offshore structures is formulated. The environmental load
due to ocean current and random waves is obtained using Morison's
equa tion. The random waves are formulated using the
Pierson-Moskowitz spectrum with the Airy linear wave theory."
This Symposium, and these Proceedings, provided a forum for the
latest thinking in analytical, computational and experimental
modelling of structures interacting with fluid environments. A
meaningful and lasting dialogue was facilitated between leading
researchers in the different component disciplines. It is intended
that, through these dialogues, multidisciplinary linkages will be
establishes leading to integrated approaches to modelling the
complex, nonlinear interactions between fluids and structures.
Examples of classes of interactions that may be addressed in this
Symposium include ocean structures, fluid conveying structures, and
aerospace structures. The energy transfer processes are inherently
nonlinear in all aspects of the behaviour. The important class of
vortex-induced oscillations has regions of lock-in, where the
structural natural frequencies rather than the fluid velocity
govern the shedding, and there exists hysteretic behaviour.
A large body of engineering and engineering science is concerned
about fluid-structure interactions. Yet there are many unanswered
questions about the underlying physics, so much so that a great
deal of empiricism remains. Much of this empiricism can be traced
to the relative lack of detailed collaboration between the fluid
and structural mechanics communities studying these interactions.
Generally, it has been that structural mechanicians would place
extensive effort into the structural model, while a simple
oscillator represented fluid motions. Conversely, fluid
mechanicians placed most of their modelling efforts into the fluid,
often considering the structure to be a rigid single degree of
freedom oscillator. While such studies havesignificantly increased
understanding, it appears that the next breakthroughs in the field
need to be modelled at a comparable lever of accuracy.
The real fluid-structure system is one of complex exchanges of
forces and energies, resulting in highly nonlinear behaviours. The
ability to model, solve and test fully coupled fluid-structure
systems portends a rich and profound understanding. In fact, recent
research efforts have indeed started to focus on the development of
fully coupled models. This Symposium is therefore a response to
these new and exciting developments in the field.
Bringing together some of the most recognized and influential
researchers and scientists in various space-related disciplines,
Lunar Settlements addresses the many issues that surround the
permanent human return to the Moon. Numerous international
contributors offer their insights into how certain technological,
physiological, and psychological challenges must be met to make
permanent lunar settlements possible. The book first looks to the
past, covering the Apollo and Saturn legacies. In addition, former
astronaut and U.S. Senator Harrison H. Schmitt discusses how to
maintain deep space exploration and settlement. The book then
discusses economic aspects, such as funding for lunar commerce,
managing human resources, and commercial transportation logistics.
After examining how cultural elements will fit into habitat design,
the text explores the physiological, psychological, and ethical
impact of living on a lunar settlement. It also describes the
planning/technical requirements of lunar habitation, the design of
both manned and modular lunar bases, and the protection of lunar
habitats against meteoroids. Focusing on lunar soil mechanics, the
book concludes with discussions on lunar concrete, terraforming,
and using greenhouses for agricultural purposes. Drawing from the
lunar experiences of the six Apollo landing missions to the many
American and Soviet robotic missions to current space activities
and research, this volume summarizes the problems, prospects, and
practicality of enduring lunar settlements. It reflects the key
disciplines, including engineering, physics, architecture,
psychology, biology, and anthropology, that will play significant
roles in establishing these settlements.
This plenary paper and the accompanying presentation have
highlighted field problems involving fluid-structure interaction
over a wide span of Navy operations. Considering the vast size and
versatility of the Navy's inventory, the cases presented represent
examples of a much larger problem. But even this limited set
provides sufficient evidence that fluid-structure interaction does
hinder the Navy's ability to accomplish its missions. This survey
has also established that there are no accurate and generally
applicable design tools for addressing these problems. In the
majority of cases the state-of-practice is to either make ad-hoc
adjustments and estimates based on historical evidence, or conduct
expensive focused tests directed at each specific problem and/or
candidate solution. Unfortunately, these approaches do not provide
insight into the fundamental problem, and neither can be considered
reliable regarding their likelihood of success. So the
opportunities for applying computational fluid-structure
interaction modeling to Navy problems appear limitless. Scenarios
range from the "simple" resonant strumming of underwater and in-air
cables, to the "self-contained" flow field and vibration of
aircraft/ordnance bodies at various Mach numbers, to violent
underwater transient detonations and local hull structural
collapse. Generally applicable and computationally tractable
design-oriented models for these phenomena are of course still far
in the future. But the Navy has taken the first steps in that
direction by sponsoring specialized numerical models, validation
experiments tailored for specific applications, and conferences
such as this one."
The expansion of our civilization to the Moon and beyond is now
within our reach, technically, intellectually and financially.
Apollo was not our last foray into the Solar System and already
science fiction is finding it difficult to keep ahead of science
and engineering fact. In 1807, few people anticipated the Wright
Brothers' human flight a hundred years later. In 1869, only science
fiction writers would have suggested landing people on the Moon in
1969. Similarly, other great inventions in mechanics and in
electronics were not envisaged and therefore the technologies to
which those inventions gave birth were only foreseen by a tiny
group of visionaries.
Designing a habitat for the lunar surface? You will need to know
more than structural engineering. There are the effects of
meteoroids, radiation, and low gravity. Then there are the
psychological and psychosocial aspects of living in close quarters,
in a dangerous environment, far away from home. All these must be
considered when the habitat is sized, materials specified, and
structure designed. This book provides an overview of various
concepts for lunar habitats and structural designs and
characterizes the lunar environment - the technical and the
nontechnical. The designs take into consideration psychological
comfort, structural strength against seismic and thermal activity,
as well as internal pressurization and 1/6 g. Also discussed are
micrometeoroid modeling, risk and redundancy as well as probability
and reliability, with an introduction to analytical tools that can
be useful in modeling uncertainties.
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