Modeling supersonic jet screech. I - Vortical instability wave modeling

1995 ◽  
Author(s):  
Alan Cain ◽  
William Bower ◽  
Steven Walker ◽  
Mary Lockwood
Keyword(s):  
Supersonic Jet ◽  
Instability Wave ◽  
Wave Modeling

Physics and Prediction of Supersonic Jet Noise

1994 ◽  
Vol 47 (6S) ◽  
pp. S184-S187
Author(s):  
Christopher K. W. Tam
Keyword(s):  
Supersonic Jet ◽  
Jet Noise ◽  
Supersonic Jets ◽  
Wave Radiation ◽  
Instability Wave ◽  
Empirical Constant ◽  
Supersonic Jet Noise ◽  
Turbulence Structures ◽  
Mixing Noise ◽  
Dominant Part

Both the large turbulence structures and the fine scale turbulence of the flows of supersonic jets are sources of turbulent mixing noise. At moderately high supersonic Mach numbers especially for hot jets, the dominant part of the noise is generated directly by the large turbulence structures. The large turbulence structures propagate downstream at supersonic velocities relative to the ambient sound speed. They generate strong Mach wave radiation analogous to a supersonically travelling wavy wall. A stochastic instability wave model theory of the large turbulence structures and noise of supersonic jets has recently been developed. The theory can predict both the spectrum and directivity of the dominant part of supersonic jet noise up to a multiplicative empirical constant. Calculated results agree well with measurements.

scholarly journals Supersonic Jet Noise Reductions Predicted With Increased Jet Spreading Rate

1998 ◽  
Vol 120 (3) ◽  
pp. 471-476 ◽  
Author(s):  
Milo D. Dahl ◽  
Philip J. Morris
Keyword(s):  
Supersonic Jet ◽  
Jet Noise ◽  
Spreading Rate ◽  
Operating Conditions ◽  
Instability Wave ◽  
Noise Levels ◽  
Radiation Model ◽  
Radiated Noise ◽  
Noise Radiation ◽  
Mixing Noise

In this paper, predictions are made of noise radiation from single, supersonic, axisymmetric jets. We examine the effects of changes in operating conditions and the effects of simulated enhanced mixing that would increase the spreading rate of the jet shear layer on radiated noise levels. The radiated noise in the downstream direction is dominated by mixing noise and, at higher speeds, it is well described by the instability wave noise radiation model. Further analysis with the model shows a relationship between changes in spreading rate due to enhanced mixing and changes in the far field radiated peak noise levels. The calculations predict that enhanced jet spreading results in a reduction of the radiated peak noise level.

Numerical study of supersonic jet and instability wave

1997 ◽  
Author(s):  
San-Yih Lin ◽  
Yu-Fen Chen ◽  
San-Yih Lin ◽  
Yu-Fen Chen
Keyword(s):  
Numerical Study ◽  
Supersonic Jet ◽  
Instability Wave

scholarly journals Towards Prediction and Control of Large Scale Turbulent Structure Supersonic Jet Noise

2009 ◽  
Author(s):  
Robert H. Schlinker ◽  
Ramons A. Reba ◽  
John C. Simonich ◽  
Tim Colonius ◽  
Kristjan Gudmundsson ◽  
...  
Keyword(s):  
Large Scale ◽  
Deterministic Model ◽  
Near Field ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Shear Layers ◽  
Instability Wave ◽  
Turbulent Structures ◽  
Turbulence Structures ◽  
Scale Turbulence

In this paper, we report on progress towards developing physics-based models of sound generation by large-scale turbulent structures in supersonic jet shear layers generally accepted to be the source of aft-angle noise. Aside from obtaining better engineering prediction schemes, the development and optimization of long term jet noise reduction strategies based on controlling instability wave generated large-scale turbulence structures in the shear layer can be more successful if based on predictive flow-noise models, rather than on build and test approaches alone. Such models, if successful, may also provide a path by which laboratory scale demonstrations can be more reliably translated to engine scale. Results show that the noise radiated by large-scale structures in turbulent jet shear layers may be modeled using a RANS based PSE method and projected to the far-field using a Kirchhoff surface approach. A key enabler in this procedure is the development of near-field microphone arrays capable of providing the pressure statistics needed to validate the instability wave models. Our framework provides, for the first time, a deterministic model that will allow understanding and predicting noise radiated by large-scale turbulence.

Sound generated by instability waves of supersonic flows. Part 2. Axisymmetric jets

1984 ◽  
Vol 138 ◽  
pp. 273-295 ◽  
Author(s):  
Christopher K. W. Tam ◽  
Dale E. Burton
Keyword(s):  
Near Field ◽  
Supersonic Jet ◽  
Sound Field ◽  
Supersonic Jets ◽  
Instability Wave ◽  
Experimental Measurements ◽  
Axial Distribution ◽  
Noise Sources ◽  
Instability Waves ◽  
Method Of Solution

A solution describing the spatial evolution of small-amplitude instability waves and their associated sound field of axisymmetric supersonic jets is found using the method of matched asymptotic expansions (see Part 1, Tam & Burton 1984). The inherent axisymmetry of the problem allows the instability waves to be decomposed into azimuthal wave modes. In addition, it is found that because of the cylindrical geometry of the problem the gauge functions of the inner expansion, unlike the case of two-dimensional mixing layers, are no longer just powers of ε. Instead they contain logarithmic terms. To test the validity of the theory, numerical results of the solution are compared with the experimental measurements of Troutt (1978) and Troutt & McLaughlin (1982). Two series of comparisons at Strouhal numbers 0.2 and 0.4 for a Mach-number 2.1 cold supersonic jet are made. The data compared include hot-wire measurements of the axial distribution of root-mean-squared jet centreline mass-velocity fluctuations and radial and axial distributions of near-field pressure-level contours measured by microphones. The former is used to test the accuracy of the inner (or instability-wave) solution. The latter is used to verify the correctness of the outer solution. Very favourable overall agreements between the calculated results and the experimental measurements are found. These very favourable agreements strongly suggest that the method of solution developed in Part 1 paper is indeed valid. Furthermore, they also offer concrete support to the proposition made previously by a number of investigators that instability waves are important noise sources in supersonic jets.

Supersonic jet spectrometry of chemical species resulting from thermal decomposition of polystyrene and polycarbonate

1992 ◽  
Vol 64 (19) ◽  
pp. 931A-940A ◽  
Author(s):  
Totaro Imasaka ◽  
Masami Hozumi ◽  
Nobuhiko Ishibashi
Keyword(s):  
Thermal Decomposition ◽  
Supersonic Jet ◽  
Chemical Species
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