Further Progress in Noise Source Identification in High Speed Jets via Causality Principle

Panda, Jayanta; Seasholtz, Richard G.; Elam, Kristie A.

doi:10.2514/6.2003-3126

Cited by 10 publications

(15 citation statements)

References 15 publications

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“…In all the cases reported, the correlations decrease as the Mach number is reduced from M = 0.9 down to M = 0.6. This trend is in agreement with the experimental data of Hurdl et al 16 and Panda et al 23,24 Furthermore the correlations are higher at the low Reynolds number Re D = 1700 than at the high Reynolds numbers Re D ≥ 10 5 . These effects of the Mach and Reynolds numbers are clearly illustrated in figure 8 by the axial variations of the peak of C|ω|p for the different jets.…”

Section: Case M 40 /Axissupporting

confidence: 92%

“…Schaffar 22 indeed observed maximum broadband correlations with pressure at 30 o to the jet axis of about 0.06 for points on the jet axis just downstream of the jet core. More recently, Panda et al 23,24 measured cross-correlations between the radiated pressure and flow quantities such as density and velocity fluctuations, for jets at Mach numbers 0.95 and 1.8. They observed higher correlation levels at M = 1.8, and shown the sharp fall of the maximum correlation with the radiation angle.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of sound sources in subsonic jets using causality methods on LES data

Bogey

Bailly

2005

11th AIAA/CEAS Aeroacoustics Conference

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Noise sources are investigated in subsonic jets at Mach numbers M = 0.6 and M = 0.9, with Reynolds numbers ReD = 1700 and ReD ≥ 10 5 , using data provided by Large Eddy Simulations (LES). The cross-correlations between signals of the radiated sound pressure and turbulence signals along jet axis and shear layer are in particular calculated. The normalized correlations are found to be significant, around 0.10, between the pressure radiated in the downstream direction and the centerline flow quantities. In the cases involving the sideline pressure or flow quantities along the shear layer, the correlations are much smaller. The maximum correlations are observed on the jet axis just at the end of the potential core, and fall at large emission angles. Furthermore the correlations appear to be lower as the Mach number is reduced, and to be enhanced as the Reynolds number is decreased. These correlations can be expected to be mostly due to the noise source radiating downstream, which may thus be located on the jet centerline at the end of the potential core. This flow region is moreover characterized by a dominant frequency over a large axial distance and by a high level of intermittency.

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Section: Case M 40 /Axissupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Investigation of sound sources in subsonic jets using causality methods on LES data

Bogey

Bailly

2005

11th AIAA/CEAS Aeroacoustics Conference

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“…Experimental sound source localizations [41] shown for instance that most of the downstream noise is generated just downstream of the potential core. Significant direct correlations have also been found between the downstream pressure and the flow fluctuations on the jet axis at the end of the potential core, experimentally by Schaffar [42] and Panda et al [43,44] and from the present simulation results [45].…”

Section: Discussion On Sound Sourcessupporting

confidence: 79%

Investigation of downstream and sideline subsonic jet noise using Large Eddy Simulation

Bogey

Bailly

2006

Theor. Comput. Fluid Dyn.

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The sound fields radiated by Mach number 0.6 and 0.9, circular jets with Reynolds numbers varying from 1.7 × 10 3 to 4 × 10 5 are investigated using Large Eddy Simulations. As the Reynolds number decreases, the properties of the sound radiation do not change significantly in the downstream direction, whereas they are modified in the sideline direction. At low Reynolds numbers, for large angles downstream from the jet axis, the acoustic levels are indeed remarkably lower and a large high-frequency part of the sound spectra vanishes. For all Reynolds numbers, the downstream and the sideline sound spectra both appear to scale in frequency with the Strouhal number. However their peak amplitudes vary following two different velocity exponents according to the radiation direction. The present observations suggest the presence of two sound sources: a Reynolds number-dependent source, predominant for large radiation angles, connected to the randomlydeveloping turbulence, and a deterministic source, radiating downstream, related to a mechanism intrinsic to the jet geometry, which is still to be comprehensively described. This view agrees well with the experimental results displaying two distinguishable components in turbulent mixing noise [1,2]. Keywords

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“…(14)(15)(16)(17) can be generalized by replacing |dρ/dr | by |(∇ū) · (∇ρ)|/|∇ū| and that density gradient correction is incorporated only if (∇ū) · (∇ρ) is negative. Here ∇ū is taken as the reference direction as far as density gradient effect is concerned.…”

Section: Noise Spectrum For Hot Jetsmentioning

confidence: 99%

Fine-Scale Turbulence Noise from Hot Jets

2005

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Experimental measurements indicate that the noise radiated from a jet depends not just on the jet-exit velocity alone, but is significantly affected by the jet temperature. Now, there is evidence to support the proposition that jet mixing noise consists of two principal components. These are the noise from the large turbulence structures of the jet flow and the fine-scale turbulence. The prediction of fine-scale turbulence noise from hot jets is considered. Earlier Tam and Auriault (Tam, C. K. W., and Auriault, L., "Jet Mixing Noise from Fine-Scale Turbulence," AIAA Journal, Vol. 37, No. 2, 1999, pp. 145-153) developed a semi-empirical theory capable of predicting the fine-scale turbulence noise from cold to moderate temperature jets. In this work, their semi-empirical theory is extended to high-temperature jets, up to a temperature ratio above that of present day commercial engines. The density gradient present in hot jets promotes the growth of Kelvin-Helmholtz instability in the jet mixing layer. This causes a higher level of turbulent mixing and stronger turbulence fluctuations. In addition, recent experiments reveal that the two-point space-time correlation function of turbulent mixing for hot jets is substantially different from that for cold jets. The eddy decay time is shorter, and the eddy size is slightly reduced. These changes have an appreciable impact on the noise radiated. In the present extended fine-scale turbulence theory, both effects are taken into account. Extensive comparisons between computed noise spectra and measurements for hot jets over the Mach-number range of 0.5-2.0 are reported here. Good agreements are found over inlet angle from 50 to 110 deg. This is the directivity for which fine-scale turbulence noise is dominant.

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Further Progress in Noise Source Identification in High Speed Jets via Causality Principle

Cited by 10 publications

References 15 publications

Investigation of sound sources in subsonic jets using causality methods on LES data

Investigation of sound sources in subsonic jets using causality methods on LES data

Investigation of downstream and sideline subsonic jet noise using Large Eddy Simulation

Fine-Scale Turbulence Noise from Hot Jets

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