Enhancing Sonar Performance Through Flow Control

The principal objective of, this effort shall be to demonstrate techniques which shall reduce the of fect of f low noise on the performance of sonar on underwater vehicles, and which permit effective operation at higher speeds. Flow over a sonar which is installed at the bow of an axisymmetric vehicle may be laminar, transitional, or turbulent, dependent upon the speed of the body, the pressure gradient (shaping) of the body, surface roughness, and the presence or absence of boundary layer control. Special techniques to reduce wall pressure and shear fluctuations may involve either laminarization, of the boundary layer (through body shaping or distributed, auction)' or I control of structures in the transitional or turbulent boundary layer (through injection of polymer, water, or gas) . The effectiveness of these different approaches over a range of frequencies and Reynolds numbers shall be demonstrated, using a prediction- methodology which has been validated with- experimental data (with and without application of boundary layer control techniques) from both the United States and the for Soviet Union. Approaches shall I be evaluated in terms of level of reduction of wall fluctuations, required volumes of onboard material, power requirements, and difficulty of practical application.