scholarly journals Assessing the Power of Intensity Interaction between the Solid and Fluid Phases in the Unconsolidated Water-Saturated Sandy Marine Sediments at Shear Wave Propagation

2021 ◽  
Vol 37 (1) ◽  
Author(s):  
V. A. Lisyutin ◽  
O. R. Lastovenko ◽  
◽  
Keyword(s):  
Wave Propagation ◽  
Shear Wave ◽  
Attenuation Coefficient ◽  
Marine Sediments ◽  
Pore Space ◽  
Equation Of Motion ◽  
Relative Movement ◽  
Two Phase ◽  
Dissipative Effects ◽  
Sandy Sediments

Purpose. Propagation of a shear wave in sandy marine sediments is considered. The acoustic properties of a shear wave are the phase velocity and the attenuation coefficient. It is known that in dry sandy sediments, the attenuation coefficient is directly proportional to frequency. In the saturated mediums, there are the deviations from this law that implies existence of two physical mechanisms of losses – the intergranular friction and viscous loss. The study is aimed at developing a two-phase theoretical model of the shear wave propagation in the unconsolidated marine sediments, and at identifying the dissipative effects caused by the fluid relative movement in the pore space. Methods and Results. The intergranular friction is modeled using a springpot, which represents an element combing conservative properties of a spring and dissipative ones of a dashpot. The equation of motion is applied, where a part of fluid is assumed to be associated with the media solid phase and another part is considered to be mobile. For a harmonic displacement, the equations of state and the equation of motion yield a new two-phase dispersion relation (the theory of Grain Shearing + + Effective Density, or GS + EDs, for short). The results of the GS + EDs theory are compared with the data of the velocity and attenuation measurements taken from the open sources. It is shown that during propagation of the compressional and shear waves, the mechanisms of interaction between the granules, and between the granules and fluid are not similar. Character of the changes in the grain-tograin friction parameters when the pore space is saturated with fluid, is analyzed. Conclusion. Manifestation of the dissipative effects resulting from the pore saturation with fluid depends on the density of the granules packing. In case of a dense packing, there are no conditions for the fluid relative movement, and the sandy sediments exhibit the property of a constant Q-factor. If the packing is loose, the viscous losses make a significant contribution, and the attenuation frequency dependence is nonlinear. The effective pore sizes for the compression and shear waves do not coincide.

scholarly journals Assessing the Power of Intensity Interaction between the Solid and Fluid Phases in the Unconsolidated Water-Saturated Sandy Marine Sediments at Shear Wave Propagation

2021 ◽  
Vol 28 (1) ◽  
Author(s):  
V. A. Lisyutin ◽  
O. R. Lastovenko ◽  
◽  
Keyword(s):  
Wave Propagation ◽  
Shear Wave ◽  
Attenuation Coefficient ◽  
Marine Sediments ◽  
Pore Space ◽  
Equation Of Motion ◽  
Relative Movement ◽  
Two Phase ◽  
Dissipative Effects ◽  
Sandy Sediments

Purpose. Propagation of a shear wave in sandy marine sediments is considered. The acoustic properties of a shear wave are the phase velocity and the attenuation coefficient. It is known that in dry sandy sediments, the attenuation coefficient is directly proportional to frequency. In the saturated mediums, there are the deviations from this law that implies existence of two physical mechanisms of losses – the intergranular friction and viscous loss. The study is aimed at developing a two-phase theoretical model of the shear wave propagation in the unconsolidated marine sediments, and at identifying the dissipative effects caused by the fluid relative movement in the pore space. Methods and Results. The intergranular friction is modeled using a springpot, which represents an element combing conservative properties of a spring and dissipative ones of a dashpot. The equation of motion is applied, where a part of fluid is assumed to be associated with the media solid phase and another part is considered to be mobile. For a harmonic displacement, the equations of state and the equation of motion yield a new two-phase dispersion relation (the theory of Grain Shearing + Effective Density, or GS + EDs, for short). The results of the GS + EDs theory are compared with the data of the velocity and attenuation measurements taken from the open sources. It is shown that during propagation of the compressional and shear waves, the mechanisms of interaction between the granules, and between the granules and fluid are not similar. Character of the changes in the grain-to-grain friction parameters when the pore space is saturated with fluid, is analyzed. Conclusions. Manifestation of the dissipative effects resulting from the pore saturation with fluid depends on the density of the granules packing. In case of a dense packing, there are no conditions for the fluid relative movement, and the sandy sediments exhibit the property of constant Q-factor. If the packing is loose, the viscous losses make a significant contribution, and the attenuation frequency dependence is nonlinear. The effective pore sizes for the compression and shear waves do not coincide.

In situ measurements of compressional and shear wave propagation in marine sediments and comparison to geoacoustic models

2018 ◽  
Vol 144 (3) ◽  
pp. 1960-1960
Author(s):  
Kevin M. Lee ◽  
Megan S. Ballard ◽  
Andrew R. McNeese ◽  
Gabriel R. Venegas ◽  
Preston S. Wilson
Keyword(s):  
Wave Propagation ◽  
Shear Wave ◽  
Marine Sediments ◽  
In Situ Measurements

Attenuation in fine‐grained marine sediments: Extension of the Biot‐Stoll model by the “effective grain model” (EGM)

Geophysics ◽  
1997 ◽  
Vol 62 (5) ◽  
pp. 1465-1479 ◽  
Author(s):  
Klaus C. Leurer
Keyword(s):  
Clay Minerals ◽  
Marine Sediments ◽  
Solid Phase ◽  
Pore Space ◽  
Two Phase ◽  
Flow Process ◽  
Swelling Clay ◽  
Fine Grained ◽  
Grain Model ◽  
Swelling Clay Minerals

It is postulated that the presence of swelling clay minerals in unconsolidated fine‐grained saturated marine sediments leads to deviations from the normally assumed ideal elasticity of the solid phase. In the proposed “effective grain model” (EGM), the elastic grain material is consequently replaced by an effective medium made up of a homogeneous elastic mineral phase that is isotropically interspersed with cylindrical, “penny‐shaped” inclusions of low aspect ratio representing the intracrystalline water layers in the swelling clay minerals. The two‐phase nature of the grain material thus specified results in a wave‐energy consuming squirt‐flow process from the inclusions into the pore space. Introducing the EGM into the Biot‐Stoll model (BSM) via the complex bulk modulus of the dissipative grain material leads to a better fit to literature data on the attenuation of compressional waves than does the original BSM alone. Since swelling clay minerals occur in nearly all clay‐bearing sediments, it is concluded that the attenuation mechanism of the EGM may represent a universal contribution to the overall intrinsic anelasticity of unconsolidated fine‐grained saturated marine sediments in the frequency range from a few kilohertz to about 1 MHz.

Time Domain Simulations on a Single Point Moored Submerged Sphere of Variable Radius

2005 ◽  
Author(s):  
Joa˜o M. B. P. Cruz ◽  
Anto´nio J. N. A. Sarmento
Keyword(s):  
Wave Propagation ◽  
Time Domain ◽  
Physical Phenomenon ◽  
Single Point ◽  
Vertical Direction ◽  
Equation Of Motion ◽  
Hydrodynamic Coefficients ◽  
Energy Converter ◽  
Submerged Sphere ◽  
The Time Domain

This paper presents a different approach to the work developed by Cruz and Sarmento (2005), where the same problem was studied in the frequency domain. It concerns the same sphere, connected to the seabed by a tension line (single point moored), that oscillates with respect to the vertical direction in the plane of wave propagation. The pulsating nature of the sphere is the basic physical phenomenon that allows the use of this model as a simulation of a floating wave energy converter. The hydrodynamic coefficients and diffraction forces presented in Linton (1991) and Lopes and Sarmento (2002) for a submerged sphere are used. The equation of motion in the angular direction is solved in the time domain without any assumption about its output, allowing comparisons with the previously obtained results.

Shock–like structure of phase-change flow in porous media

1981 ◽  
Vol 104 ◽  
pp. 467-482 ◽  
Author(s):  
L. A. Romero ◽  
R. H. Nilson
Keyword(s):  
Porous Media ◽  
Phase Change ◽  
Single Phase ◽  
Flow In Porous Media ◽  
Two Phase ◽  
Flows In Porous Media ◽  
Dissipative Effects ◽  
Condensing Flows ◽  
Self Similar ◽  
Phase Change Flows

Shock-like features of phase-change flows in porous media are explained, based on the generalized Darcy model. The flow field consists of two-phase zones of parabolic/hyperbolic type as well as adjacent or imbedded single-phase zones of either parabolic (superheated, compressible vapour) or elliptic (subcooled, incompressible liquid) type. Within the two-phase zones or at the two-phase/single-phase interfaces, there may be steep gradients in saturation and temperature approaching shock-like behaviour when the dissipative effects of capillarity and heat-conduction are negligible. Illustrative of these shocked, multizone flow-structures are the transient condensing flows in porous media, for which a self-similar, shock-preserving (Rankine–Hugoniot) analysis is presented.

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