Jet engine noise source location: The polar correlation technique

Fisher, Michael J.; Harper-Bourne, Marcus; Glegg, Stewart

doi:10.1016/s0022-460x(77)80111-9

Cited by 194 publications

(88 citation statements)

References 3 publications

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“…The resulting method is based on the coherence, rather than the cross-spectrum, of the pressure field. This idea represents an extension of concepts presented in the seminal paper on polar correlation technique by Fisher et al 2 In addition, we present two methods for improving the fidelity of imaging. The first method involves deconvolution of the beamforming output.…”

Section: Introductionmentioning

confidence: 90%

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Imaging of directional distributed noise sources

Papamoschou

2011

Journal of Sound and Vibration

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This study relates to the imaging of noise sources that are distributed and strongly directional, such as in turbulent jets. The goal is to generate noise source maps that are self-consistent, i.e., their integration over the extent of the noise source region gives the far-field pressure autospectrum for a particular emission direction. This is possible by including a directivity factor in the formulation of the source cross-spectral density. The resulting source distribution is based on the complex coherence, rather than the cross-spectrum, of the measured acoustic field. For jet noise, which is not only directional but whose nature changes with emission angle, it is necessary to conduct the measurements with a narrow-aperture array. The resulting images must be devoid to the extent possible of spatial distortions caused by the array response. Two methods for obtaining clean images are addressed: deconvolution of the beamformer output and direct spectral estimation. The two techniques produced similar noise source maps for a Mach 0.9 cold jet.

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Section: Introductionmentioning

confidence: 90%

“…A similar formulation was proposed by Fisher et al 2 to account for the directivity of jet noise in the implementation of the polar correlation technique. Equation 8 thus takes the form…”

Section: Formulation Of Directional Source Distributionmentioning

confidence: 99%

Imaging of directional distributed noise sources

Papamoschou

2011

Journal of Sound and Vibration

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“…It is now universally admitted that this mixing noise is generated by the turbulence of the flow and that the noise producing region is axially restricted to about two potential core lengths (Fisher et al, 1977;Laufer et al, 1976). Turbulence is separated in this region in small turbulent eddies, with small dimensions compared to the nozzle, and large-scale structures.…”

Section: Introductionmentioning

confidence: 99%

Simulation of Flow Control with Microjets for Subsonic Jet Noise Reduction

Huet¹,

Rahier²,

Vincent³

2012

Applied Aerodynamics

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“…The majority of the turbulent mixing noise that originates from large structure dynamics emanates from a region that surrounds the end of the potential core. This determination has been made with an examination of the far-field acoustic radiation with a variety of microphone arrays [e.g.. Fisher et al 1977, Venkatesh et al 2003] as well as an examination of the near-field pressure [Tam 1991]. One has to understand the dynamics of the large sfructures to understand how they generate noise because a time-dependent phenomenon is required for the generation of sound [Lighthill 1952, 1954, Crighton 1975, Lilley 1991.…”

Section: Introductionmentioning

confidence: 99%

Correlation of Flow Structures and Radiated Noise in High Speed Jets

Samimy¹,

Hileman²,

Caraballo³

et al. 2004

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, search! the collection of information. Send comments regarding tNs burden estimate or any other aspect of tNs collection of information, including suggest!The dynamics of large-scale turbulence structures within a high Reynolds number, ideally expanded Mach 1.3 jet were investigated during both the periods of production of strong acoustic radiation and extended periods of relative quiet that lacked such acoustic radiation. These results were acquired through a unique experiment where the sources of large amplitude sound waves were estimated with a three-dunensional microphone array and the flow field was simultaneously visualized on two orthogonal planes. The images from one of the planes were taken at a 167 kHz rate. Proper Orthogonal Decomposition (POD) was employed to create a basis of the size and distribution of large-scale structures within the two planes. These POD modes were then used to objectively determine the differences in the jet structure during noise generation and periods lacking significant noise generation. The results show that the flow during the periods of relative quiet cases is dominated by the lower order POD modes that consist of relatively large turbulence structures while it is dominated by higher order POD modes that capture the dynamic mterplay of the large-scale structures durmg noise generation periods. For approximately one convective time scale prior to the moment of noise emission, a series of large-scale structures forms and disintegrates within the mixing layer and in the process a large amount of ambient fluid is entramed into the core of the jet. For the first time, these results show how the dynamic interplay of large-scale turbulence structures generates acoustic radiation within a high Reynolds number jet. SUBJECT TERMS ABSTRACTThe dynamics of large-scale turbulence structures within a high Reynolds number, ideally expanded Mach 1.3 jet were investigated during both the periods of production of strong acoustic radiation and extended periods of relative quiet that lacked such acoustic radiation. These results were acquired through a unique experiment where the sources of large amplitude sound waves were estimated with a three-dimensional microphone array and the flow field was simultaneously visualized on two orthogonal planes. The images from one of the planes were taken at a 167 kHz rate. Proper Orthogonal Decomposition (POD) was employed to create a basis of the size and distribution of large-scale structures within the two planes. These POD modes were then used to objectively determine the differences in the jet structure during noise generation and periods lacking significant noise generation. The results show that the flow during the periods of relative quiet cases is dominated by the lower order POD modes that consist of relatively large turbulence structures while it is dominated by higher order POD modes that cap...

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Jet engine noise source location: The polar correlation technique

Cited by 194 publications

References 3 publications

Imaging of directional distributed noise sources

Imaging of directional distributed noise sources

Simulation of Flow Control with Microjets for Subsonic Jet Noise Reduction

Correlation of Flow Structures and Radiated Noise in High Speed Jets

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