Mechanical Chevrons and Fluidics for Advanced Military Aircraft Noise Reduction
NAVAL RESEARCH LAB WASHINGTON DC
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There is a growing need to reduce significantly the noise generated by high-performance, supersonic military aircraft. The noise generated during takeoff and landing on aircraft carriers has direct impact on shipboard health and safety issues. Noise complaints are increasing as communities move closer to military bases or when there are changes due to base closures and realignment. Furthermore, U.S. and international noise regulations and policies will have an impact on military operations and training unless we take effective steps to reduce the noise. In response to a statement of need WPSON-07-04 identified by SERDP, the Naval Research laboratory NRL in collaboration with the University of Cincinnati UC and GE Aircraft Engines, proposed a three-year research program investigating the use of mechanical chevrons and fluidics for reducing the noise from supersonic military jet aircraft. The technical approach adopted was a combined experimental and computational study. This final technical report provides details of the studies conducted and the results obtained. First, we show that the numerical simulations can accurately predict the details of the flow field and noise generated by supersonic jets from nozzles that are representative of military jet aircraft engine nozzles. Then, we use the numerical simulations and complementary experiments to derive further information on the source of noise from supersonic jets under a variety of operating conditions. With the benefit of this knowledge, we investigate and report on the potential of mechanical chevrons and three fluidics-based techniques to reduce the noise. We find that each of the techniques investigated are capable of providing significant noise reduction but further studies are needed to optimize these techniques and assess a tradeoff between various factors such as cost of implementation, potential impact on performance and benefits derived.