Control of Jet Noise Through Mixing Enhancement

The idea of using mixing enhancement to reduce jet noise is not new. Lobed mixers have been around since shortly after jet noise became a problem. However, these designs were often a post-design fix that rarely was worth its weight and thrust loss from a system perspective. Recent advances in CFD and some inspired concepts involving chevrons have shown how mixing enhancement can be successfully employed in noise reduction by subtle manipulation of the nozzle geometry. At NASA Glenn Research Center, this recent success has provided an opportunity to explore our paradigms of jet noise understanding, prediction, and reduction. Recent advances in turbulence measurement technology for hot jets have also greatly aided our ability to explore the cause and effect relationships of nozzle geometry, plume turbulence, and acoustic far field. By studying the flow and sound fields of jets with various degrees of mixing enhancement and subsequent noise manipulation, we are able to explore our intuition regarding how jets make noise, test our prediction codes, and pursue advanced noise reduction concepts. The paper will cover some of the existing paradigms of jet noise as they relate to mixing enhancement for jet noise reduction, and present experimental and analytical observations that support these paradigms.

[1]  W. N. Dalton,et al.  AST Critical Propulsion and Noise Reduction Technologies for Future Commercial Subsonic Engines: Separate-Flow Exhaust System Noise Reduction Concept Evaluation , 2000 .

[2]  James Bridges,et al.  Study of three-stream laboratory jets with passive mixing enhancements for noise reduction , 2000 .

[3]  P. Morris,et al.  Calculation of sound propagation in nonuniform flows: Suppression of instability waves , 2004 .

[4]  Abbas Khavaran,et al.  On the Applicability of High-Frequency Approximations to Lilley's Equation , 2004 .

[5]  Jonathan Gilson,et al.  Prediction of three dimensional jet noise , 2001 .

[6]  J. Seiner,et al.  On the Two Components of Turbulent Mixing Noise from Supersonic Jets , 1996 .

[7]  Anurag Agarwal,et al.  The Calculation of Sound Propagation in Nonuniform Flows: Suppression of Instability Waves , 2003 .

[8]  Thomas J. Barber,et al.  Advanced Subsonic Technology (AST) Separate-Flow High-Bypass Ratio Nozzle Noise Reduction Program Test Report , 2000 .

[9]  H. V. Fuchs,et al.  On turbulence and noise of an axisymmetric shear flow , 1975, Journal of Fluid Mechanics.

[10]  James Bridges,et al.  Acoustics and Thrust of Quiet Separate-Flow High-Bypass-Ratio Nozzles , 2003 .

[11]  C. Tam,et al.  Jet Mixing Noise from Fine-Scale Turbulence , 1998 .

[12]  Victor F. Kopiev,et al.  Vortex ring eigen-oscillations as a source of sound , 1997, Journal of Fluid Mechanics.

[13]  A. Khavaran.  Role of anisotropy in turbulent mixing noise , 1999 .

[14]  E. A. Krejsa,et al.  Computation of supersonic jet mixing noise for an axisymmetric convergent-divergent nozzle , 1994 .

[15]  Jonathan B. Freund,et al.  Jet Noise Physics and Modeling Using First-principles Simulations , 2003 .

[16]  James Bridges,et al.  A Parametric Study of Fine-Scale Turbulence Mixing Noise , 2002 .

[17]  Tim Colonius,et al.  On the Noise Generated by Shear-Layer Instabilities in Turbulent Jets , 2003 .