Calculation of the acoustic field of an angle transducer in the far-field zone

The sound generated by vortex pairing in a two-dimensional compressible mixing layer is investigated. Direct numerical simulations (DNS) of the Navier–Stokes equations are used to compute both the near-field region and a portion of the acoustic field. The acoustic analogy due to Lilley (1974) is also solved with acoustic sources determined from the near-field data of the DNS. It is shown that several commonly made simplifications to the acoustic sources can lead to erroneous predictions for the acoustic field. Predictions based on the quadrupole form of the source terms derived by Goldstein (1976a, 1984) are in excellent agreement with the acoustic field from the DNS. However, despite the low Mach number of the flow, the acoustic far field generated by the vortex pairings cannot be described by considering compact quadrupole sources. The acoustic sources have the form of modulated wave packets and the acoustic far field is described by a superdirective model (Crighton & Huerre 1990). The presence of flow–acoustic interactions in the computed source terms causes the acoustic field predicted by the acoustic analogy to be very sensitive to small changes in the description of the source.

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Reprint of: Extension of the near acoustic field of a jet to the far field

Procedia IUTAM ◽

10.1016/j.piutam.2010.10.002 ◽

2010 ◽

Vol 1 ◽

pp. 9-18

Author(s):

Christopher K.W. Tam ◽

Nikolai N. Pastouchenko ◽

K. Viswanathan

Keyword(s):

Acoustic Field ◽

Far Field

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A Combined Finite Element Method with Normal Mode for the Elastic Structural Acoustic Radiation in Shallow Water

Journal of Theoretical and Computational Acoustics ◽

10.1142/s2591728520500048 ◽

2020 ◽

Vol 28 (04) ◽

pp. 2050004

Author(s):

Buchao An ◽

Chao Zhang ◽

Dejiang Shang ◽

Yan Xiao ◽

Imran Ullah Khan

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Shallow Water ◽

Normal Mode ◽

Acoustic Field ◽

Acoustic Radiation ◽

Three Dimensional ◽

Far Field ◽

Azimuthal Direction ◽

Element Method

A combined Finite Element Method with Normal Mode (FEM-NM) is proposed for calculation of the acoustic field radiated by a three-dimensional structural source in shallow water. The FEM is used to calculate the near range acoustic field, then the modes expansion at the vertical and azimuthal direction is performed at a certain coupling range. Hence, the true three-dimensional acoustic field at any range is obtained rapidly by the NM theory. The numerical examples show the efficiency and accuracy of this method. The coupling range and the truncation of the vertical modes hardly affect the far field results.

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Potentialities of optical data processing in the far field zone by volume holograms

Soviet Journal of Quantum Electronics ◽

10.1070/qe1977v007n06abeh012873 ◽

1977 ◽

Vol 7 (6) ◽

pp. 681-685

Author(s):

R Güther ◽

S Kusch

Keyword(s):

Data Processing ◽

Optical Data ◽

Far Field ◽

Field Zone ◽

Optical Data Processing ◽

Volume Holograms

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Obtaining Unipolar Pulses at Far Field Zone of the Source

Optics and Spectroscopy ◽

10.1134/s0030400x21090034 ◽

2021 ◽

Author(s):

M. V. Arkhipov ◽

R. M. Arkhipov ◽

N. N. Rosanov

Keyword(s):

Far Field ◽

Field Zone

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Acoustic scattering by a finite rigid plate with a poroelastic extension

Journal of Fluid Mechanics ◽

10.1017/jfm.2016.59 ◽

2016 ◽

Vol 791 ◽

pp. 414-438 ◽

Cited By ~ 36

Author(s):

Lorna J. Ayton

Keyword(s):

Noise Reduction ◽

Acoustic Field ◽

Wind Turbines ◽

Acoustic Scattering ◽

Leading Edge ◽

Chord Length ◽

Far Field ◽

Rigid Plate ◽

Acoustic Source ◽

Trailing Edge

The scattering of sound by a finite rigid plate with a finite poroelastic extension interacting with an unsteady acoustic source is investigated to determine the effects of porosity, elasticity and the length of the extension when compared to a purely rigid plate. The problem is solved using the Wiener–Hopf technique, and an approximate Wiener–Hopf factorisation process is implemented to yield reliable far-field results quickly. Importantly, finite chord-length effects are taken into account, principally the interaction of a rigid leading-edge acoustic field with a poroelastic trailing-edge acoustic field. The model presented discusses how the poroelastic trailing-edge property of owls’ wings could inspire quieter aeroacoustic designs in bladed systems such as wind turbines, and provides a framework for analysing the potential noise reduction of these designs.

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