are interesting and challenging. While specialization within the field has become more common, in the past its leaders distinguished themselves by applying their skills across the entire field. Lighthill, for example, made seminal contributions to aerodynamics, gas dynamics, acoustics, biofluidynamics, and meteorology.

The only supporter of hydromechanics research of any import is ONR. However, during the 1990s, ONR, and especially that part of ONR most relevant for naval hydromechanics, became more mission-oriented. That is, it became more concerned with solving specific problems over short time scales than with developing new knowledge that will support naval forces well into the twenty-first century. In view of federal budget constraints, this focus on the short term is understandable, but because of time constraints and limited horizons, short-term, mission-oriented research almost always becomes a synthesis of current knowledge rather than a generator of new knowledge. Individuals attracted to research are more excited by discovery than by synthesis, so the academic pipeline of younger researchers feeding into naval hydromechanics research is directly affected by the relative emphasis that ONR places on fundamentals.

In 1956 the Mechanics Division of the ONR used its resources to sponsor the first Symposium on Naval Hydrodynamics. The list of contributors to that first symposium attested to the significance of the field: Milne-Thomson, Lighthill, Stoker, Munk, Longuet-Higgins, Wehausen, Benjamin, Birkhoff, Strasberg, Batchelor, Gilbarg, Plesset, Lin, Klebanoff, and Corrsin. Barely a decade after World War II and well into the Cold War, the need to maintain naval superiority was never far from the minds of those scientists who could contribute to the field. But they were not scientists who made their reputations doing mission-oriented research—they were scientists who attacked problems having broad implications and applications, and they changed their field in the most fundamental ways. Having scientists and engineers of this stature making contributions to the Navy Department's needs in hydromechanics was ONR's goal in the 1950s and should again become its goal today.

Over the past 30 years there has been a substantial reduction in the number of programs in naval architecture, but this should not be interpreted as evidence that naval hydromechanics is a fully mature field. For example, although the equations describing hydromechanical flows are well established, they are nonlinear and can be solved analytically only for rather special flows or when linear approximations are adequate. However, important hydromechanics problems can be solved only by numerical methods (see “Computational Simulation of Hydromechanics Phenomena” in Chapter 3). Furthermore, because very different scales can be involved, modeling of the subgrid scale physics is often required, and this presents significant computational challenges. When wave breaking, air entrainment, cavitation, and turbulence are important, as they are in many naval hydromechanics problems, the modeling and computation are more difficult, and current capabilities are not adequate. Thus there are both needs and opportunities for research in naval hydromechanics. But because it is not a field in its infancy, it is more difficult to make rapid advances than it was 30 years ago, so research is even more essential to progress than it was in the past.

Distribution of Research Performers

Naval hydromechanics research is conducted in three types of institutions: academic, government, and private. The list of FY99 principal investigators in the hydromechanics programs of ONR 333, the Mechanics and Energy Conversion S&T Division, provides insights into the distribution of hydromechanics research across these institutions.

Nearly every university department of engineering, physics, or mathematics could be included as a potential performer of hydromechanics research. In the ONR tabulation, 63 of 101 projects were



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