Measurement of Source Wave-Packets in High-Speed Jets and Connection to Far-Field Sound

Reba, Ramons; Simonich, J. C.; Schlinker, R. H.; Hartford, E.

doi:10.2514/6.2008-2891

Cited by 27 publications

(20 citation statements)

References 10 publications

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“…Consistent with our previous studies [5], we interpret these fluctuations as average wave-packet amplitudes. We note that the cross-correlation analysis (not shown here but reported earlier in [48] for a subsonic jet) supports the interpretation in that the pressure fluctuations are highly correlated at all positions along the array depicted in the figure.…”

Section: Theoretical Mechanism Of Noise Reductionsupporting

confidence: 86%

“…Motivated by our results linking instability waves/wave packets and peak noise radiation in simple round jets, a wave-packet-based diagnostic technique was further developed to address nonaxisymmetric jet flows of technological relevance, including chevron nozzles and jets forced at higher azimuthal modes [48]. The novel hydrodynamic nearfield rotating array concept employs two linear arrays: one fixed, and the second free to rotate azimuthally (see Figs.…”

Section: E Microphone Arraysmentioning

confidence: 99%

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Active Control of Noise from Hot Supersonic Jets

Sinha¹,

Towne²,

Colonius³

et al. 2018

AIAA Journal

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This paper presents diagnostic experiments aimed at understanding and mitigating supersonic jet noise from the coherent wave-packet structures that are the source of peak aft-angle mixing noise. Both isothermal and heated, nearly perfectly expanded, Mach 1.5 jets were forced in the near-nozzle region with air injection generated by a spinning-valve device designed to excite the jet at frequencies approaching those of the dominant turbulent structures. Substantial reductions in the peak aft-angle radiation were achieved with steady blowing at amplitudes corresponding to 2-6% of the mass flow rate of the primary jet. The noise benefit saturated at mass flow rates above 4%, with as much as a 6 dB reduction in overall sound pressure level at aft angles. Increasing the mass flow rates yielded a monotonically increasing high-frequency noise penalty at the sideline, where noise levels in the natural jet were already 15 dB lower than the aft-angle peak, so that the penalty due to actuation was minor. Although both steady and periodic unsteady mass injections were produced by the spinning valve when it rotated, it was calibrated to hold the steady mass flow rate constant as the frequency of unsteady blowing was changed. In this way, the effect of steady and unsteady blowings on the acoustic field could be decoupled. It is shown that the noise benefit was uniquely associated with the steady component of blowing, whereas the unsteady component resulted in additive tones in the spectra. This implied linearity is consistent with theory and experiments showing that the wave-packet structures, which give rise to the dominant aft-angle radiation, evolve in the turbulent mean flowfield in a nearly linear fashion from their origin in the near-nozzle region. The interpretation of noise reduction is that the steady component of blowing spreads the mean flow more rapidly, resulting in weaker wave packets. Periodic unsteady blowing forces coherent wave packets that are largely uncorrelated from the random natural ones, which then leads to the observed additive tones.

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Section: Theoretical Mechanism Of Noise Reductionsupporting

confidence: 86%

Section: E Microphone Arraysmentioning

confidence: 99%

Active Control of Noise from Hot Supersonic Jets

Sinha¹,

Towne²,

Colonius³

et al. 2018

AIAA Journal

Self Cite

View full text Add to dashboard Cite

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“…The result therefore provides evidence, complementary to the work of Suzuki & Colonius (2006) and Reba, Simonich & Schlinker (2008) but going beyond it, in the following ways: (a) we did not explicitly set out to find instability waves; (b) we educe and study both the velocity and the pressure components of the field; (c) we use the far-field sound to perform the eduction; and (d) we extract space-and time-dependent fields. The work allows us to conclude that the low-angle far-field sound is driven by the dynamics of linear instabilities.…”

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confidence: 69%

Educing the source mechanism associated with downstream radiation in subsonic jets

et al. 2012

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This work belongs to the ongoing debate surrounding the mechanism responsible for low-angle sound emission from subsonic jets. The flow, simulated by large eddy simulation (Bogey & Bailly, Comput. Fluids, vol. 35 (10), 2006a, pp. 1344-1358, is a Mach 0.9 jet with Reynolds number, based on the exit diameter, of 4 × 10 5 . A methodology is implemented to educe, explore and model the flow motions associated with low-angle sound radiation. The eduction procedure, which is based on frequency-wavenumber filtering of the sound field and subsequent conditional analysis of the turbulent jet, provides access to space-and time-dependent (hydrodynamic) pressure and velocity fields. Analysis of these shows the low-angle sound emission to be underpinned by dynamics comprising space and time modulation of axially coherent wavepackets: temporally localized energization of wavepackets is observed to be correlated with the generation of high-amplitude acoustic bursts. Quantitative validation is provided by means of a simplified line-source Ansatz (Cavalieri et al. J. Sound Vib., vol. 330, 2011b, pp. 4474-4492). The dynamic nature of the educed field is then assessed using linear stability theory (LST). The educed pressure and velocity fields are found to compare well with LST: the radial structures of these match the corresponding LST eigenfunctions; the axial evolutions of their fluctuation energy are consistent with the LST amplification rates; and the relative amplitudes of the pressure and velocity fluctuations, which are educed independently of one another, are consistent with LST.

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“…Other approaches have focused on near-field pressure. A summary of the early approaches is given in [29]. While these studies represent significant advances toward revealing noise mechanisms in high-speed jets, they were unable to (quantitatively) project sound levels in the far-field using measured near-field source information.…”

Section: Experimental Approachmentioning

confidence: 99%

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

Schlinker¹,

Reba²,

Simonich³

et al. 2009

Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Controls, Diagnostics and Instrumentation; Education;

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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.

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Measurement of Source Wave-Packets in High-Speed Jets and Connection to Far-Field Sound

Cited by 27 publications

References 10 publications

Active Control of Noise from Hot Supersonic Jets

Active Control of Noise from Hot Supersonic Jets

Educing the source mechanism associated with downstream radiation in subsonic jets

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

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