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

Bogey, Christophe; Bailly, Christophe

doi:10.2514/6.2005-2885

Cited by 21 publications

(15 citation statements)

References 35 publications

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“…The experimental results of Panda et al are consistent with the earlier observations of Hurdle, Meecham & Hodder (1974) and Schaffar (1979). In addition, the more recent correlation estimations by Bogey & Bailly (2005) using numerical simulation data computed by LES methodology also yielded very similar conclusions. Evidently, all these results are in support of the proposition that there are two noise sources in a high-speed jet.…”

Section: A(x)supporting

confidence: 80%

The sources of jet noise: experimental evidence

Tam¹,

et al. 2008

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The primary objective of this investigation is to determine experimentally the sources of jet mixing noise. In the present study, four different approaches are used. It is reasonable to assume that the characteristics of the noise sources are imprinted on their radiation fields. Under this assumption, it becomes possible to analyse the characteristics of the far-field sound and then infer back to the characteristics of the sources. The first approach is to make use of the spectral and directional information measured by a single microphone in the far field. A detailed analysis of a large collection of far-field noise data has been carried out. The purpose is to identify special characteristics that can be linked directly to those of the sources. The second approach is to measure the coherence of the sound field using two microphones. The autocorrelations and cross-correlations of these measurements offer not only valuable information on the spatial structure of the noise field in the radial and polar angle directions, but also on the sources inside the jet. The third approach involves measuring the correlation between turbulence fluctuations inside a jet and the radiated noise in the far field. This is the most direct and unambiguous way of identifying the sources of jet noise. In the fourth approach, a mirror microphone is used to measure the noise source distribution along the lengths of high-speed jets. Features and trends observed in noise source strength distributions are expected to shed light on the source mechanisms. It will be shown that all four types of data indicate clearly the existence of two distinct noise sources in jets. One source of noise is the fine-scale turbulence and the other source is the large turbulence structures of the jet flow. Some of the salient features of the sound field associated with the two noise sources are reported in this paper.

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Section: A(x)supporting

confidence: 80%

The sources of jet noise: experimental evidence

Tam¹,

et al. 2008

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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: 67%

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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“…The experimental results of Panda et al 8 are consistent with the earlier observations of Hurdle et al 9 (Mach 0.99 and 0.85 jets) and Schaffar 10 (Mach 0.98 jet). In addition, the more recent correlation measurements by Bogey and Bailly 11 using numerical simulation data computed by large-eddy simulation methodology also yielded very similar conclusions. Evidently, all of these results are in support of the suggestion 3−6 that there are two noise sources in a high-speed jet.…”

Section: Introductionsupporting

confidence: 58%