The role of instability waves in predicting jet noise

Goldstein, M. E.; Leib, S. J.

doi:10.1017/s0022112004002551

Cited by 58 publications

(37 citation statements)

References 25 publications

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“…However, we now have to question the relevance of these conclusions for turbulent jets, as they were based on initially laminar or transitional jets. In fact, the subsequent analytical work of Goldstein & Leib (2005) lends support to the earlier (and present) view of the importance of linear instability waves of the turbulent mean flow field in determining the dominant aft angle sound radiation.…”

Section: Introductionsupporting

confidence: 67%

Wavepacket models for supersonic jet noise

et al. 2014

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Gudmundsson and Colonius (J. Fluid Mech., vol. 689, 2011, pp. 97-128) have recently shown that the average evolution of low-frequency, low-azimuthal modal large-scale structures in the near field of subsonic jets are remarkably well predicted as linear instability waves of the turbulent mean flow using parabolized stability equations. In this work, we extend this modelling technique to an isothermal and a moderately heated Mach 1.5 jet for which the mean flow fields are obtained from a high-fidelity large-eddy simulation database. The latter affords a rigourous and extensive validation of the model, which had only been pursued earlier with more limited experimental data. A filter based on proper orthogonal decomposition is applied to the data to extract the most energetic coherent components. These components display a distinct wavepacket character, and agree fairly well with the parabolized stability equations model predictions in terms of near-field pressure and flow velocity. We next apply a Kirchhoff surface acoustic propagation technique to the near-field pressure model and obtain an encouraging match for far-field noise levels in the peak aft direction. The results suggest that linear wavepackets in the turbulence are responsible for the loudest portion of the supersonic jet acoustic field.

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Section: Introductionsupporting

confidence: 67%

Wavepacket models for supersonic jet noise

et al. 2014

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“…However the basic mechanism of this sound source is still subject to discussion. The generation of noise by the rapid growth and decay of instability waves in the jet was for instance proposed and investigated analytically [8,9]. It is interesting to notice that this mechanism is likely to generate a highly directional radiation.…”

Section: Discussion On Sound Sourcesmentioning

confidence: 99%

“…The presence of these two components is supported by the works of Tam et al [2,4] and Viswanathan [6,7] who identified two independent self-similar spectra from a large experimental database of sound spectra. That of a sound source connected to the growing and decaying instability waves is also suggested by analytical works [8,9]. This view of two noise components is attractive, but it suffers from the confusing data available in the literature, whose trends can vary between different experiments because of acoustic contamination [10] or of the use of one-third octave spectra [11].…”

Section: Introductionmentioning

confidence: 96%

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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“…Such observations have since prompted many attempts at modeling turbulent coherent structures as linear instability modes of the time-averaged flow field -the Kelvin-Helmholtz instability. As examples, we cite the works of Crighton & Gaster (1976), Mankbadi & Liu (1984), Tam & Burton (1984), and Goldstein & Leib (2005). Recent rigorous validations, made possible by the current availability of detailed experimental data and well-validated large-eddy simulation (LES) databases, have leant renewed credence to the linear stability model .…”

Section: Introductionmentioning

confidence: 99%

Parabolized stability analysis of jets from serrated nozzles

et al. 2016

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We study the viscous spatial linear stability characteristics of the time-averaged flow in turbulent subsonic jets issuing from serrated (chevroned) nozzles, and compare them to analogous round jet results. Linear parabolized stability equations (PSE) are used in the calculations to account for the non-parallel base flow. By exploiting the symmetries of the mean flow due to the regular arrangement of serrations, we obtain a series of coupled two-dimensional PSE problems from the original three-dimensional problem. This reduces the solution cost and manifests the symmetries of the stability modes. In the parallel-flow linear stability theory (LST) calculations that are performed near the nozzle to initiate the PSE, we find that the serrated nozzle reduces the growth rates of the most unstable eigenmodes of the jet, but their phase speeds are approximately similar. We obtain encouraging validation of our linear PSE instability wave results vis-à-vis near-field hydrodynamic pressure data acquired on a phased microphone array in experiments, after filtering the latter with proper orthogonal decomposition (POD) to extract the energetically dominant coherent part. Additionally, a large-eddy simulation database of the same serrated jet is investigated, and its POD-filtered pressure field is found to compare favourably with the corresponding PSE solution within the jet plume. We conclude that the coherent hydrodynamic pressure fluctuations of jets from both round and serrated nozzles are reasonably consistent with the linear instability modes of the turbulent mean flow.

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The role of instability waves in predicting jet noise

Cited by 58 publications

References 25 publications

Wavepacket models for supersonic jet noise

Wavepacket models for supersonic jet noise

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

Parabolized stability analysis of jets from serrated nozzles

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