Acoustic Identification of Coherent Structures in a Turbulent Jet

Guj, G.; Carley, Michael; Camussi, Roberto; Ragni, A.

doi:10.1006/jsvi.2002.5130

Cited by 60 publications

(38 citation statements)

References 34 publications

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“…The loud flow structures of both LR-OID mode pairs are in qualitative agreement with experiments (see e.g. Juvé et al 1980;Guj, Carley & Camussi 2003;Hileman et al 2004;Coiffet et al 2006). In figure 10(g-l), the first six LE-OID modes are shown.…”

Section: Acoustically Optimized Oid Of Jet Flowsupporting

confidence: 83%

On least-order flow representations for aerodynamics and aeroacoustics

et al. 2012

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We propose a generalization of proper orthogonal decomposition (POD) for optimal flow resolution of linearly related observables. This Galerkin expansion, termed 'observable inferred decomposition' (OID), addresses a need in aerodynamic and aeroacoustic applications by identifying the modes contributing most to these observables. Thus, OID constitutes a building block for physical understanding, leastbiased conditional sampling, state estimation and control design. From a continuum of OID versions, two variants are tailored for purposes of observer and control design, respectively. Firstly, the most probable flow state consistent with the observable is constructed by a 'least-residual' variant. This version constitutes a simple, easily generalizable reconstruction of the most probable hydrodynamic state to preprocess efficient observer design. Secondly, the 'least-energetic' variant identifies modes with the largest gain for the observable. This version is a building block for Lyapunov control design. The efficient dimension reduction of OID as compared to POD is demonstrated for several shear flows. In particular, three aerodynamic and aeroacoustic goal functionals are studied: (i) lift and drag fluctuation of a two-dimensional cylinder wake flow; (ii) aeroacoustic density fluctuations measured by a sensor array and emitted from a two-dimensional compressible mixing layer; † Email address for correspondence: michael.schlegel@tu-berlin.de

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Section: Acoustically Optimized Oid Of Jet Flowsupporting

confidence: 83%

On least-order flow representations for aerodynamics and aeroacoustics

et al. 2012

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“…This wave-packet behavior (Figure 9) is correlated with temporally localized bursts of sound in the far field (Cavalieri et al 2011a, Guj et al 2003, Hileman et al 2005, Juvé et al 1980, Kerhervé et al 2012b, Koenig et al 2012). Recent optimal-control studies provide further confirmation.…”

Section: Intermittency: Loud and Quiet Flowsmentioning

confidence: 94%

“…A final important characteristic of the far field is its temporal intermittency. Noise is observed to recur at St ≈ 0.2 in temporally localized bursts, a behavior that can be detected using time-local analysis (Cavalieri et al 2011a, Guj et al 2003, Hileman et al 2005, Juvé et al 1980 or characterized with a wavelet basis (Koenig et al 2012).…”

Section: Jet-noise Sensitivity To Upstream Conditionsmentioning

confidence: 99%

Wave Packets and Turbulent Jet Noise

Jordan

Colonius

2013

Annu. Rev. Fluid Mech.

526

299

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Turbulent jet noise is a controversial fluid mechanical puzzle that has amused and bewildered researchers for more than half a century. Whereas numerical simulations are now capable of simultaneously predicting turbulence and its radiated sound, the theoretical framework that would guide noise-control efforts is incomplete. Wave packets are intermittent, advecting disturbances that are correlated over distances far exceeding the integral scales of turbulence. Their signatures are readily distinguished in vortical turbulence; the irrotational, evanescent near field; and the propagating far field. We review evidence of the existence, energetics, dynamics, and acoustic efficiency of wave packets. We highlight how extensive data available from simulations and modern measurement techniques can be used to distill acoustically relevant turbulent motions. The evidence supports theories that seek to represent wave packets as instability waves, or more general modal solutions of the governing equations, and confirms the acoustic importance of these structures in the aft-angle radiation of high subsonic and supersonic jets. The resulting unified view of wave packets provides insights that can help guide control strategies.

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“…Even without reference to the preceding discussion on the efficacy of vortex sound as framework for understanding jet noise, a few researchers have chosen to look at the acoustic far-field with the assumption that at least some of the sources of noise are intermittent [e.g. 6,[27][28][29][30][31][32][33][34]. A common theme that unifies these works is the use of wavelet analysis -the underlying principle of which is that the signals under examination cannot be adequately described by a set of periodic waves.…”

Section: Iib Temporally Localized Signal Analysismentioning

confidence: 99%

“…It was also shown that when the amplitude of the events was artificially reduced via signal post-processing, the amplitude of the spectral peak could be reduced by several decibels. Guj et al [32] used a similar kind of conditional averaging of the flow-field to determine that bursts of noise were related to dynamically significant fluctuations of the large-scale structures. They also called attention to the limitations of Fourier analysis to illuminate this kind of phenomenon.…”

Section: Iib Temporally Localized Signal Analysismentioning

confidence: 99%

Time-Domain Analysis of Subsonic Jet Noise

Kearney-Fischer

Sinha

Samimy

2012

50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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Following on previous works showing that jet noise has significant intermittent aspects, the present work assumes that these intermittent events are the dominant feature of jet noise. A definition and method of detection for intermittent noise events is devised and implemented. Using a large experimental database of acoustically subsonic jets with different acoustic Mach numbers (M a = 0.5 -0.9), diameters (D = 2.54, 5.08, & 7.62 cm), and exit temperature ratios (ETR = 0.84 -2.70), these events are extracted from the noise signals measured in the anechoic chamber of the NASA Glenn AeroAcoustic Propulsion Laboratory. It is shown that a signal containing only these events retains all of the important aspects of the acoustic spectrum for jet noise radiating to shallow angles relative to the jet downstream axis, validating the assumption that intermittent events are the essential feature of low angle jet noise. The characteristics of these noise events are analyzed showing that these events can be statistically described in terms of three parameters (the variance of the original signal, the mean width of the events, and the mean time between events) and two universal statistical distribution curves. The variation of these parameters with radiation direction, diameter, velocity, and temperature are discussed. A simple model for this kind of signal is formulated and used to derive a relationship between the characteristics of the noise events and the fluctuations in the integrated noise source volume.

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Acoustic Identification of Coherent Structures in a Turbulent Jet

Cited by 60 publications

References 34 publications

On least-order flow representations for aerodynamics and aeroacoustics

On least-order flow representations for aerodynamics and aeroacoustics

Wave Packets and Turbulent Jet Noise

Time-Domain Analysis of Subsonic Jet Noise

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