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An Assessment of Naval Hydromechanics Science and Technology
by turbulent boundary layers has been funded by ONR for many years. This led to an understanding of exponential attenuation of evanescent (nonradiating) hydrodynamic wave numbers, which when applied to the concept of using materials that were inefficient radiators and good transmitters led to rubber- or glass-reinforced plastic domes.
Currently, a great deal of fundamental hydromechanics research is focused on computational fluid dynamics (CFD) and the treatment of unsolved problems associated therewith: turbulence, separation, cavitation, and free-surface behavior, including bow and transom wave breaking. Such research is important since, clearly, CFD will become more powerful in the years ahead. However, general solutions to the unsolved problems are not imminent, and even if they were, they would not produce advanced platform concepts. A vital strength of such research is its ability to develop techniques that are adequate for the analysis of specific concepts and to perform such analyses. Without clearly defined concepts, there is a danger that CFD research will not be as effective as it otherwise could be (e.g., the study of highly separated flows is a challenging problem but is not particularly relevant to concepts designed to avoid or limit separation).
Certainly ONR and the Naval Sea Systems Command 05H, which includes the Hydrodynamics/ Hydroacoustics Technology Center, recognize the importance of advanced concepts. In their presentations to the committee, both organizations emphasized the importance of concept development, with specific reference to advanced shaping, advanced appendages, advanced propulsion, and advanced flow control techniques. Unfortunately, the committee could find no persuasive evidence that there is a currently planned 6.2/6.3 effort to create advanced platform concepts. None of the presentations reported any concerted efforts to explore advanced concepts, either at a subsystem or total system level. Rather, the emphasis is on transitioning design tools for current concepts, which are based primarily on computational fluid dynamics. Improvements in such tools will undoubtedly transition (i.e., be used by designers) once they have been adequately validated; such transitions are important and will at least partially satisfy the perceived pressure for near-term results. However, as noted above, these tools alone are unlikely to lead to significant advances in platform capability. If successful, their largest impact will be to reduce development cost and time.
It should be emphasized that there is no lack of need for advanced technology nor any lack of desire to produce it. In the 1997 NSB study Technology for the United States Navy and Marine Corps, 2000-2035,1 stealth was identified as a fundamental attribute for submarines. Although it was not such a priority for surface ships, signature reduction was considered to be necessary and cost-effective. Additional emphasis on stealth was articulated by the Program Executive Office-Submarines, which called the art and science of designing and building quiet submarine propulsors one of its crown jewels. Moreover, greater affordability —that is, more capability per unit cost—is always needed, and it is an area where hydromechanics can have a significant impact. In the laboratory arena, a recent review by the NSWCCD gave prominence to signature and silencing systems and hull forms and propulsors as its core assets. Yet there does not appear to be an integrated 6.2/6.3 program to bring appropriate concepts to fruition.
One reason for the lack of an integrated 6.2/6.3 program that includes development of advanced platform concepts may be the persistent lack of adequate funding. Table 5.1 and Figure 5.1 show funding for 6.2/6.3 Navy Department ship and submarine technology funding from FY82 through FY99. The funding shown in Figure 5.1 is the total of up to four program elements in each fiscal year: 0602121N, currently titled surface ship and submarine technology; 0602323N, now defunct, but titled submarine technology when it existed; 0603508N, which used to be titled ship propulsion system (advanced); and 0603573N, titled electric drive when it was a 6.3 program. The total Department of the Navy 6.2/6.3 investment for all ship and submarine technology in the FY99 President's Budget was about $100 million per year, which covers efforts in structures, internal machinery, topside signature reduction, and electromagnetic compatibility as well as hydromechanics. Although this level of funding is actually higher than representative annual investments for the past two decades, when the 6.2/6.3 effort averaged about $70 million per year, it does not seem adequate to conduct the type of technology demonstrations required for advanced platform concepts.
Naval Studies Board, National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035: Becoming a 21st-Century Force, Vol. 6, Platforms. Washington, D.C.: National Academy Press.