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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."
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.
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