Spatial attenuation of different sound field components in a water layer and shallow-water sediments

Belov, A. I.; Kuznetsov, G. N.

doi:10.1134/s1063771017050037

Cited by 9 publications

(8 citation statements)

References 7 publications

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“…Input parameters are as follows: d = 0.4 mm; ρ g = 2500 kg/m 3 ; K g = 710 10 Pa; ρ f = 968 kg/m 3 ; K f = 9.6810 8 Pa; η = 9810 -3 Pas; P = 0.36;  = 8.310 -11 m 2 ; ξ = 1.7; a 0 = 5.2510 -5 m.…”

Section: F I G 2 Hydraulic Permeability Depending On the Granules' mentioning

confidence: 99%

“…In the shallow water acoustics, a variety of more or less efficient methods of bottom research are used [2,3,[5][6][7][8][9][10][11]. All these methods in one way or another solve the problem of restoring the acoustic properties of the bottom from the sound field measured in the water layer.…”

mentioning

confidence: 99%

“…It should be noted that tonal-spatial methods should be applied with caution to determine the acoustic properties of the sediments, since the result of the inversion depends on the initially selected layered bottom model. More informative are methods based on the pulsed source field analysis in a wide frequency band [7][8][9][10]. Here, the information about the bottom contains in the dispersion-dissipative characteristics of the waveguide modes.…”

mentioning

confidence: 99%

“…Such a model of sediments and bottom well corresponds to the basic model of a shallow water waveguide, where the bottom is represented as a homogeneous half-space (Pekeris Waveguide). The half-space is the averaging of all layers, so the Pekeris model is most often used nowadays [5][6][7][8][9][10].…”

mentioning

confidence: 99%

“…When calculating sound fields at the tonal frequency the bottom representation in the liquid half-space form is often quite sufficient [2,6]. The situation changes when the task of inversion of the acoustic and physical properties of the bottom is set and calculations are required in a wide frequency band [8][9][10][11]. Here, the correct mapping of the frequency dependences of attenuation and phase velocity can be of fundamental importance.…”

mentioning

confidence: 99%

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Generalized Rheological Model of the Unconsolidated Marine Sediments with Internal Friction and Effective Compressibility

Lisyutin¹

2019

PhO

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The quasi-two-phase theory of propagation of an elastic wave in the unconsolidated marine sediments is represented. The longitudinal and shear waves can propagate in marine sediments. The phase velocities, the attenuation coefficients and their frequency dependences are the acoustic properties of these waves. It is shown experimentally that the in dry granular media, the attenuation coefficient is directly proportional to frequency. Whereas in the saturated media, the deviations from this law are noted whence it follows that there are two physical loss mechanisms: the internal and viscous friction. Data and methods. The medium in a dry state is represented as a generalized Kelvin-Voigt element consisting of a spring and a springpot that is an element combining the spring conservative properties and the dashpot dissipative properties. The wave equation and the dispersion relation including the internal friction only are deduced using the mathematical apparatus of the fractional derivatives. Then, a new two-phase equation of state is deduced, where a part of the fluid is considered to be associated with a solid phase and another part is mobile. Substitution of the equation of state into the wave equation results in a quadratic dispersion relation whose roots yield the wave numbers of two types of the waves, namely the fast and slow ones (Grain Shearing + Effective Compressibility or GS + EC theory). According to the GS + EC theory, significant sound speed dispersion and deviations of the attenuation frequency dependence upon the linear law in the mid-frequency range occur due to a change of the medium compressibility. Results. The results of the GS + EC theory are compared with the experimental measurement data on of phase velocity and attenuation taken from the open sources. It is shown that at low frequencies, the unconsolidated medium is of greater compressibility than at high ones that is a result of the fluid displacement from the pore space narrowing. Discussion and conclusion. Viscous dissipation is manifested at the medium frequencies, when the fluid is still mobile and the viscous forces are rather significant. At high frequencies, the granules and the fluid oscillate together, and attenuation in the medium arises due to the forces of the internal friction.

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Section: F I G 2 Hydraulic Permeability Depending On the Granules' mentioning

confidence: 99%