Surface wave modes on elastic cylinders

Frisk, George V.; Dickey, J.; Überall, H.

doi:10.1121/1.380755

Cited by 61 publications

(23 citation statements)

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“…The physical interpretation of resonances inside an impenetrable bubble can be understood by realizing that the Bessel functions represent standing waves formed by incoming and outgoing waves in the radial direction such that (3) where . Using the asymptotic expansion for as given by [17], one finds (4) where are coefficients, is the Gamma function, and . The factor is a result of waves propagating through caustics.…”

Section: Cnr's For Impenetrable Spheres and Bubblesmentioning

confidence: 99%

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Electromagnetic resonances of immersed dielectric spheres

Chen

1998

IEEE Trans. Antennas Propagat.

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Section: Cnr's For Impenetrable Spheres and Bubblesmentioning

confidence: 99%

“…These poles are related to surface propagating waves (creeping waves) [3]. The same wave mechanisms are also called "Franz waves" for acoustic scattering from a "rigid sphere" in fluids [4], [5]. This type of wave propagates in the external medium and is mainly determined by the surface geometry instead of the interior material property.…”

mentioning

confidence: 99%

Electromagnetic resonances of immersed dielectric spheres

Chen

1998

IEEE Trans. Antennas Propagat.

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“…Among all the targets of simple geometrical forms (plate, cylinder, sphere, tube...), tubes are the subject of few studies of characterization [1][2][3][4][5][6][7][8][9][10][11][12]. If an air-filled tube immersed in water is excited by a plane acoustic wave perpendicularly to its axis, circumferential waves are generated in the shell and in the water/shell interface [13,14]. For some frequencies, these circumferential waves form stationary waves on the circumference of the tube constituting resonances [14].…”

Section: Introductionmentioning

confidence: 99%

“…If an air-filled tube immersed in water is excited by a plane acoustic wave perpendicularly to its axis, circumferential waves are generated in the shell and in the water/shell interface [13,14]. For some frequencies, these circumferential waves form stationary waves on the circumference of the tube constituting resonances [14]. The mode n of a resonance is the number of wavelengths around the circumference.…”

Section: Introductionmentioning

confidence: 99%

A Neuro-fuzzy Computing Technique for Modeling the Acoustic Form Function of Immersed Tubes

Nahraoui¹,

Aassif²,

Elhanaoui³

et al. 2013

IJCA

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An Adaptative Neuro-Fuzzy Inference System (ANFIS) is developed to predict the acoustic form function (FF) for an infinite length cylindrical shell excited perpendicularly to its axis. The Wigner-Ville distribution (WVD) is used like a comparison tool between the calculated FF by the analytical method and that predicted by the neuro-fuzzy technique for a copper tube. During the application of this technique, several configurations are evaluated for various radius ratio b/a (a: outer radius, b: inner radius of tube). This neuro-fuzzy technique is able to predict the FF with a mean relative error (MRE) about 1.7%.

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“…While this solution may converge more quickly than the normal mode solution, the zeros must still be found numerically. The disadvantages of this method are that it is not a total solution (unless all of the zeros are found) and that the numerical search for the poles may be complicated, especially for small cylinder radii (Frisk et al, 1975;Grace and Goodman, 1966). Numerical experiments have verified theoretical results (and vice versa) for both the total field solutions and for individual contributions to the scattered field (Brill and Uberall, 1970;Faran, 1951;Neubauer et al, 1974;Stoyanov et al, 1989).…”

Section: Introductionmentioning

confidence: 99%

Ocean bottom seismic scattering

Dougherty¹

1989

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Seismic studies of the oceanic crust, both experimental and theoretical, often assume a flat seafloor and laterally homogeneous crust. This is done regardless of the appearance in seismic data of obvious effects due to scattering from lateral heterogeneities both on and in the seafloor. Detailed fine scale surveys of mid-ocean ridges, where the upper oceanic crust is exposed, have revealed the presence of lateral heterogeneities in the form of complicated topography, extrusive volcanic structure, and abundant fracturing and faulting. These heterogeneities have a significant affect on the propagation of seismo/acoustic energy through the crust, especially in the immediate vicinity of the seafloor. This thesis deals with the problem of scattering of seismo/acoustic energy from a number of forms of lateral heterogeneity in the upper oceanic crust.A common theme throughout this work is that the size of the heterogeneity on or in the seafloor is of the same order of magnitude as the seismo/acoustic wavelength. This is the realm of scattering theory where the wave-like characteristics of seismic energy have a particularly large influence on the outcome of interaction with structure in the media. The work presented here involves the application of the finite difference modeling technique to problems concerning laterally heterogeneous elastic media. This method is a full wave solution to the elastic wave equation and as such includes all wave interactions with the media. The finite difference formulation is used to study four distinct phenomena; scattering from discrete deterministic seafloor features; wave propagation through continuous randomly heterogeneous upper oceanic crust; scattering from more complicated topographic profiles and the limitations of the method for the rough seafloor problem; and the problem of plane acoustic wave scattering from an infinite elastic cylinder.The principal finding of this work is that lateral heterogeneities in the upper oceanic crust can have a dramatic affect on seismo/acoustic wave propagation. Scattering from rough seafloors and/or volume heterogeneities is often quite similar and causes the occurrence of signal generated 'noise' (coda), decorrelation of primary arrivals, and anomalies in arrival travel time and amplitude. Topographic and volume scatterers acting as secondary sources of seismic energy can cause a resonant coupling of body wave energy into interface (Stoneley) waves at the seafloor. This is possibly one mechanism by which natural seismic and storm generated acoustic energy can be coupled into seafloor noise.The applicability of the use of the finite difference method for non-planar watersolid interfaces is also discussed. Models were calculated which approximate sinusoidal seafloors and plane acoustic wave scattering from an infinite elastic cylinder. The discretization of a rectangular difference grid must be extremely fine to accurately accommodate a smoothly varying water-solid interface which does not align with the grid. Regardless of the discretiza...

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Surface wave modes on elastic cylinders

Cited by 61 publications

References 0 publications

Electromagnetic resonances of immersed dielectric spheres

Electromagnetic resonances of immersed dielectric spheres

A Neuro-fuzzy Computing Technique for Modeling the Acoustic Form Function of Immersed Tubes

Ocean bottom seismic scattering

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