Correlations of Jet Noise Azimuthal Components and Their Role in Source Identification

Kopiev, V. F.; Chernyshev, S. L.; Faranosov, G. A.; Zaitsev, M. Yu.; Belyaev, I. V.

doi:10.2514/6.2010-4018

Cited by 17 publications

(17 citation statements)

References 8 publications

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“…With this we have a phenomenological interpretation linking the actuation to the far field. We note that the results of a number of other jet-noise control studies are consistent with this: noise abatement is most efficient when flows are driven with high ω-m combinations (Samimy et al 2007;Kopiev et al 2010). While we cannot affirm that the mean fields are in those cases stable to such actuation, this does seem likely, as the canonical mean field of a round subsonic jet is most stable to high frequencies and high azimuthal wavenumbers.…”

Section: Analysis and Interpretationsupporting

confidence: 72%

“…4.1. The quieter flow: stabilisation of axisymmetric wavepackets We first consider the quieter St p = 0.46 case, and note that the greatest noise reduction is observed at low emission angles, where the sound field is known to be predominantly axisymmetric (Juvé, Sunyach & Comte-Bellot 1979;Kopiev et al 2010;Cavalieri et al 2012a) and dominated by a source mechanism driven by the axisymmetric component of the axial velocity fluctuation (Michalke & Fuchs 1975;Cavalieri et al 2013). This sound source is considered by many to comprise an axially extended non-compact wavepacket, understood as an instability of the mean field.…”

Section: Analysis and Interpretationmentioning

confidence: 99%

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Jet-noise control by fluidic injection from a rotating plug: linear and nonlinear sound-source mechanisms

et al. 2016

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We present a study of the turbulent and acoustic fields of subsonic jets, controlled by means of a novel actuator that introduces perturbations via steady-fluidic actuation from a rotating centrebody. The actuation can produce louder or quieter jets, and these are analysed using time-resolved stereoscopic particle image velocimetry and a hot-wire anemometer. We place the analysis in the framework of wavepackets and linear stability theory, whence we show, using solutions of the linear parabolised stability equations, that the quieter flows can be understood to result from a mean-flow deformation that modifies wavepacket dynamics, and in particular their phase velocities, which are significantly reduced. The mean-flow deformation is shown, by a triple decomposition, to be due to the generation of Reynolds stresses associated with incoherent turbulence (rather than coherent structures) which arises when the actuation energises the flow with a frequency-azimuthal wavenumber (ω-m) combination to which the mean flow is stable. When the actuation excites the flow with an ω-m combination to which the mean flow is unstable, the response is dominated by coherent structures, whose rapid growth takes them beyond the linear limit, where they undergo quadratic wave interactions and lead, consequently, to a louder flow.

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Section: Analysis and Interpretationsupporting

confidence: 72%

Section: Analysis and Interpretationmentioning

confidence: 99%

Jet-noise control by fluidic injection from a rotating plug: linear and nonlinear sound-source mechanisms

et al. 2016

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“…At present, no anonymous opinion exists on how different mechanisms characterizing the dynamics of turbulent pulsations contribute to noise generation. For example, different authors consider different factors as sources of jet noise: small scale tur bulence [1][2][3][4][5][6], instability waves [6,7], and oscillations of large scale turbulent eddies [8].…”

Section: Introductionmentioning

confidence: 99%

“…At the same time, they are inconsistent with experimental noise data obtained by the azimuthal decomposition method [9], according to which subsonic jet noise is characterized by a qua drupole structure. Subsequent correlation models were also developed for quadrupole sources [3,4].…”

Section: Introductionmentioning

confidence: 99%

New correlation model for the cascade of turbulent pulsations as a noise source in jets

Kopiev

Chernyshev

2012

Acoust. Phys.

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The mechanisms of noise generation by turbulent jets associated with a cascade of turbulent per turbations are considered from generation of primary eddies to their disintegration. A new correlation model proposed for describing these mechanisms is based on simulation of their generation as a random process with deterministic description of individual eddies. The model makes it possible to analyze available correlation models based on experimental modeling of the correlation function: monopoles, dipoles, or quadrupoles. The main difference between these models is both the different multipole structure of assumed sources and implicit "hard" and "soft" variants of source generation, as well as in the main variable for which the corre lation function is developed. This approach is used for developing the correlation model of the noise genera tion mechanism related to oscillations of surface eddies. The jet noise inferred from the proposed model is well consistent with experimental data on circular jet noise.

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“…In a more recent study by Kopiev et al (2010) the azimuthal correlation of the far field noise was investigated for unexcited and tone-excited jets. However, both studies only considered a single jet Mach number and therefore did not investigate the Mach number scaling of the azimuthal modes.…”

Section: Mach Number Scaling Of Azimuthal Modes Of Subsonic Co-flowinmentioning

confidence: 99%

Mach-number scaling of individual azimuthal modes of subsonic co-flowing jets

Sandberg

Tester

2016

J. Fluid Mech.

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The Mach number scaling of the individual azimuthal modes of jet mixing noise was studied for jets in flight conditions, i.e. with co-flow. The data were obtained via a series of Direct Numerical Simulations (DNS), performed of fully turbulent jets with a target Reynolds number, based on nozzle diameter, of Re jet = 8, 000. The DNS included a pipe 25 diameters in length in order to ensure that the flow developed to a fully turbulent state before exiting into a laminar co-flow, and to account for all possible noise generation mechanisms. To allow for a detailed study of the jet-mixing noise component of the combined pipe/jet configuration, acoustic liner boundary conditions on the inside of the pipe and a modification to the synthetic turbulent inlet boundary condition of the pipe were applied to minimize internal noise in the pipe. Despite these measures, the use of a phased array source breakdown technique was essential in order to isolate the sources associated with jet noise mechanisms from additional noise sources that could be attributed to internal noise or unsteady flow past the nozzle lip, in particular for the axisymmetric mode. Decomposing the sound radiation from the pipe/jet configuration into its azimuthal Fourier modes, and accounting for the co-flow effects, it was found † Email address for correspondence: richard.sandberg@unimelb.edu.au

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Correlations of Jet Noise Azimuthal Components and Their Role in Source Identification

Cited by 17 publications

References 8 publications

Jet-noise control by fluidic injection from a rotating plug: linear and nonlinear sound-source mechanisms

Jet-noise control by fluidic injection from a rotating plug: linear and nonlinear sound-source mechanisms

New correlation model for the cascade of turbulent pulsations as a noise source in jets

Mach-number scaling of individual azimuthal modes of subsonic co-flowing jets

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