A model supersonic buried-nozzle jet: instability and acoustic wave scattering and the far-field sound

We consider sound source mechanisms involving the acoustic and instability modes of dual-stream isothermal supersonic jets with the inner nozzle buried within an outer shroud-like nozzle. A particular focus is scattering into radiating sound waves at the shroud lip. For such jets, several families of acoustically coupled instability waves exist, beyond the regular vortical Kelvin–Helmholtz mode, with different shapes and propagation characteristics, which can therefore affect the character of the radiated sound. In our model, the coaxial shear layers are vortex sheets while the incident acoustic disturbances are the propagating shroud modes. The Wiener–Hopf method is used to compute their scattering at the sharp shroud edge to obtain the far-field radiation. The resulting far-field directivity quantifies the acoustic efficiency of different mechanisms, which is particularly important in the upstream direction, where the results show that the scattered sound is more intense than that radiated directly by the shear-layer modes.

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Transmission and Far-Field Radiation of Sound Waves in and from Lined Ducts Containing Shear Flow

Aeroacoustics: Jet and Combustion Noise; Duct Acoustics ◽

10.2514/5.9781600865114.0353.0371 ◽

1975 ◽

pp. 353-371

Keyword(s):

Shear Flow ◽

Far Field ◽

Sound Waves ◽

Field Radiation ◽

Lined Ducts

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Transmission and far field radiation of sound waves in and from lined ducts containing shear flow

10.2514/6.1973-1013 ◽

1973 ◽

Cited By ~ 2

Author(s):

M. MIKHAIL ◽

A. ABDELHAMID

Keyword(s):

Shear Flow ◽

Far Field ◽

Sound Waves ◽

Field Radiation ◽

Lined Ducts

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Analysis of Sound Waves with Semi Perforated Pipe

Academic Perspective Procedia ◽

10.33793/acperpro.02.03.77 ◽

2019 ◽

Vol 2 (3) ◽

pp. 704-710

Author(s):

Burhan Tiryakioglu

Keyword(s):

Boundary Condition ◽

Fourier Transform ◽

Wave Equation ◽

Pipe Wall ◽

Far Field ◽

Sound Waves ◽

Hopf Equation ◽

Hopf Method ◽

The Fourier Transform ◽

Perforated Pipe

The paper presents analytical results of radiation phenomena at the far field and solution of the wave equation with adequate boundary condition imposed by the pipe wall. An infinite pipe with perforated part is considered. The solution is obtained by using the Fourier transform technique in conjunction with the Wiener-Hopf Method. Applying the Fourier transform technique, the boundary value problem is described by Wiener Hopf equation and then solved analytically.

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Computation of Near-Field and Far-Field Radiation Characteristics of Acoustic Transducers for Underwater Acoustic Imaging

International Journal on Communications Antenna and Propagation (IRECAP) ◽

10.15866/irecap.v10i3.18684 ◽

2020 ◽

Vol 10 (3) ◽

pp. 145

Author(s):

L. S. Praveen ◽

Govind R. Kadambi ◽

S. Malathi ◽

Preetham Shankapal

Keyword(s):

Near Field ◽

Acoustic Imaging ◽

Far Field ◽

Radiation Characteristics ◽

Underwater Acoustic ◽

Acoustic Transducers ◽

Field Radiation

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The shape of things to come — Development and testing of a new marine vibrator source

The Leading Edge ◽

10.1190/tle38090680.1 ◽

2019 ◽

Vol 38 (9) ◽

pp. 680-690 ◽

Cited By ~ 1

Author(s):

Benoît Teyssandier ◽

John J. Sallas

Keyword(s):

Seismic Source ◽

Test Facility ◽

Data Sets ◽

Far Field ◽

Ocean Bottom ◽

Air Gun ◽

Seismic Image ◽

Field Radiation ◽

Technical Issues ◽

To Come

Ten years ago, CGG launched a project to develop a new concept of marine vibrator (MV) technology. We present our work, concluding with the successful acquisition of a seismic image using an ocean-bottom-node 2D survey. The expectation for MV technology is that it could reduce ocean exposure to seismic source sound, enable new acquisition solutions, and improve seismic data quality. After consideration of our objectives in terms of imaging, productivity, acoustic efficiency, and operational risk, we developed two spectrally complementary prototypes to cover the seismic bandwidth. In practice, an array composed of several MV units is needed for images of comparable quality to those produced from air-gun data sets. Because coupling to the water is invariant, MV signals tend to be repeatable. Since far-field pressure is directly proportional to piston volumetric acceleration, the far-field radiation can be well controlled through accurate piston motion control. These features allow us to shape signals to match precisely a desired spectrum while observing equipment constraints. Over the last few years, an intensive validation process was conducted at our dedicated test facility. The MV units were exposed to 2000 hours of in-sea testing with only minor technical issues.

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6—The Instability of Two Vortex Sheets Enclosing a Subsonic Jet due to Acoustic Radiation

Proceedings of the Royal Society of Edinburgh Section A Mathematics ◽

10.1017/s0080454100009419 ◽

1974 ◽

Vol 72 (1) ◽

pp. 79-91 ◽

Cited By ~ 2

Author(s):

N. Hardisty

Keyword(s):

Acoustic Radiation ◽

Vortex Sheets ◽

Instability Waves ◽

Subsonic Jet

SummaryThe propagation of sound in a subsonic jet separated by two vortex sheets from two semi-infinite still media is considered and it is found that instability waves arise at particular points on the vortex sheets and that their effect is confined to certain regions.

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An improved method of diagnosis of failed elements in arrays based on far-field radiation pattern

2016 Progress in Electromagnetic Research Symposium (PIERS) ◽

10.1109/piers.2016.7734367 ◽

2016 ◽

Author(s):

Jing Miao ◽

Bo Chen ◽

Xiaolin Zhang ◽

Yang Chen

Keyword(s):

Radiation Pattern ◽

Far Field ◽

Improved Method ◽

Field Radiation

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Radiation from supersonic faulting

Bulletin of the Seismological Society of America ◽

10.1785/bssa0610041009 ◽

1971 ◽

Vol 61 (4) ◽

pp. 1009-1012 ◽

Cited By ~ 1

Author(s):

J. C. Savage

Keyword(s):

Initial Point ◽

Step Function ◽

Fault Model ◽

Dislocation Segment ◽

Far Field ◽

Fault Propagation ◽

Unit Step ◽

Propagation Factor ◽

Double Couple ◽

Field Radiation

abstract The far-field radiation from a simple fault model is given by the radiation pattern associated with the appropriate strain nucleus (e.g., double couple) multiplied by a fault propagation factor. For a unilateral fault model the propagation factor is F ( c ; t ) = ζ bd [ H ( τ ) − H ( τ − ( L / ζ ) ( 1 − ( ζ / c ) cos ψ )) ] / ( 1 − ( ζ / c ) cos ψ ) where ξ is the velocity of fault propagation, b is the fault slip, d is the fault width, τ = t − r0/c, r0 is the distance of the observer from the initial point of faulting, c is the velocity of the seismic wave, H(τ) is the unit-step function, L is the length of the fault, and ψ the angle between r0 and the direction of fault propagation. This representation is valid for both subsonic and supersonic fault propagation. The latter case is important because Weertman (1969) has recently shown that spontaneous faulting may propagate at supersonic velocities. Because the propagation factor is always positive, the nodal planes for the radiation are the same as for the appropriate strain nucleus. Finally, it is shown by the application of this equation that the radiation from a screw dislocation segment is represented by the double-couple nucleus, not the compensated linear-vector dipole nucleus as recently suggested by Knopoff and Randall (1970).

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