scholarly journals Shear wave dispersion and attenuation in periodic systems of alternating solid and viscous fluid layers

2006 ◽  
Vol 43 (25-26) ◽  
pp. 7673-7683 ◽  
Author(s):  
Boris Gurevich ◽  
Radim Ciz
Keyword(s):  
Viscous Fluid ◽  
Shear Wave ◽  
Wave Dispersion ◽  
Periodic Systems ◽  
Fluid Layers ◽  
Dispersion And Attenuation

scholarly journals Effect of fluid viscosity on elastic wave attenuation in porous rocks

Geophysics ◽  
2002 ◽  
Vol 67 (1) ◽  
pp. 264-270 ◽  
Author(s):  
Boris Gurevich
Keyword(s):  
Viscous Fluid ◽  
Dispersion Equation ◽  
Shear Wave ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Fluid Viscosity ◽  
Fast Wave ◽  
Compressional Waves ◽  
Dispersion Equations ◽  
Fluid Layers

Attenuation and dispersion of elastic waves in fluid‐saturated rocks due to pore fluid viscosity is investigated using an idealized exactly solvable example of a system of alternating solid and viscous fluid layers. Waves in periodic layered systems at low frequencies can be studied using an asymptotic analysis of Rytov's exact dispersion equations. Since the wavelength of the shear wave in the fluid (viscous skin depth) is much smaller than the wavelength of the shear or compressional waves in the solid, the presence of viscous fluid layers requires a consideration of higher‐order terms in the low‐frequency asymptotic expansions. This expansion leads to asymptotic low‐frequency dispersion equations. For a shear wave with the directions of propagation and of particle motion in the bedding plane, the dispersion equation yields the low‐frequency attenuation (inverse quality factor) as a sum of two terms which are both proportional to frequency ω but have different dependencies on viscosity η: one term is proportional to ω/η, the other to ωη. The low‐frequency dispersion equation for compressional waves allows for the propagation of two waves corresponding to Biot's fast and slow waves. Attenuation of the fast wave has the same two‐term structure as that of the shear wave. The slow wave is a rapidly attenuating diffusion‐type wave, whose squared complex velocity again consists of two terms which scale with iω/η and iωη. For all three waves, the terms proportional to η are responsible for the viscoelastc phenomena (viscous shear relaxation), whereas the terms proportional to η−1 account for the visco‐inertial (poroelastic) mechanism of Biot's type. Furthermore, the characteristic frequencies of visco‐elastic ωV and poroelastic ωB attenuation mechanisms obey the relation ωVωB = AωR2, where ωR is the resonant frequency of the layered system, and A is a dimensionless constant of order 1. This result explains why the visco‐elastic and poroelastic mechanisms are usually treated separately in the context of macroscopic theories that imply ω << ωR. The poroelastic mechanism dominates over the visco‐elastic one when the frequency‐indepenent parameter B = ωB/ωV = 12η2/μsρfhf2 << 1, and vice versa, where hf is the fluid layer thickness, ρf the fluid density, and μs represents the shear modulus of the solid.

Dispersion and attenuation of shear wave in couple stress stratum due to point source

2021 ◽  
pp. 107754632199888
Author(s):  
Richa Kumari ◽  
Abhishek K Singh
Keyword(s):  
Point Source ◽  
Shear Wave ◽  
Couple Stress ◽  
Imperfect Interface ◽  
Layered Composite ◽  
Functionally Graded ◽  
Function Technique ◽  
Dispersive Wave ◽  
Attenuation Profiles ◽  
Dispersion And Attenuation

This study discusses the propagation of a horizontally polarised shear wave in a layered composite structure consisting of couple stress stratum over a functionally graded orthotropic viscoelastic substrate due to point source existing at an imperfect interface of the stratum and substrate. Because of the CS effect in the stratum, the existence of the second kind of dispersive (shear) wave is established along with conventional first kind of a shear wave. The closed-form dispersion equations and damping equations of the first and second kind of a dispersive wave are derived by adopting non-traditional boundary conditions and Green’s function technique. The effect of characteristic length of microstructure, imperfect bonding parameter and functional gradient parameters on velocity profiles and attenuation profiles of the first and second kind of dispersive wave has been computed numerically and delineated graphically. For validation, established results are matched with the classical one.

An initial study of complete 2D shear wave dispersion images using a reverberant shear wave field

2019 ◽  
Vol 64 (14) ◽  
pp. 145009 ◽  
Author(s):  
Juvenal Ormachea ◽  
Kevin J Parker ◽  
Richard G Barr
Keyword(s):  
Wave Field ◽  
Shear Wave ◽  
Wave Dispersion ◽  
Initial Study

scholarly journals Wave Dispersion and Attenuation on Human Femur Tissue

Sensors ◽  
2014 ◽  
Vol 14 (8) ◽  
pp. 15067-15083 ◽  
Author(s):  
Maria Strantza ◽  
Olivia Louis ◽  
Demosthenes Polyzos ◽  
Frans Boulpaep ◽  
Danny van Hemelrijck ◽  
...  
Keyword(s):  
Wave Dispersion ◽  
Human Femur ◽  
Dispersion And Attenuation
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