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.