scholarly journals PHYSICAL MODELING OF THE ELASTIC WAVES REFLECTION FROM THE BOUNDARY WITH LOW-VELOCITY AZIMUTHALLY ANISOTROPIC MEDIUM

2020 ◽  
Vol 1 (1) ◽  
pp. 60-71
Author(s):  
K. V. Fedin ◽  
Yu. I. Kolesnikov ◽  
R. N. Beysembaev
Keyword(s):  
Anisotropic Medium ◽  
Elastic Waves ◽  
Physical Modelling ◽  
Reflection Coefficients ◽  
3D Printer ◽  
Azimuthal Dependence ◽  
Low Velocity ◽  
Isotropic Media ◽  
Theoretical Reflection ◽  
Good Agreement

The physical modelling of elastic waves reflected from the boundary between the water and the model of low-velocity azimuthally anisotropic medium was carried out. The model of anisotropic medium was made using 3D printer. The results of experiments showed that the reflection coefficients are practically independent from the azimuth at the angles of incidence less than 25°. At larger angles of incidence, the azimuthal dependence of the reflection coefficients is observed, which is most pronounced at azimuths from 45° to 75°. The results of measurements in the layering direction are in good agreement with the theoretical reflection coefficients for the boundary of isotropic media.

Compression waves reflection from the low-velocity azimuthally anisotropic medium: a physical model study

2020 ◽  
Vol 221 (2) ◽  
pp. 1320-1326
Author(s):  
YuI Kolesnikov ◽  
K V Fedin ◽  
L Ngomayezwe
Keyword(s):  
Fractured Reservoirs ◽  
Physical Modelling ◽  
Azimuthal Anisotropy ◽  
Reflection Coefficients ◽  
Low Velocity ◽  
Compression Waves ◽  
Model Study ◽  
Isotropic Media ◽  
Hti Media ◽  
High Degree

SUMMARY Interest in azimuthal anisotropy of rocks is mainly associated with fractured reservoirs, which may contain hydrocarbon deposits. Cracks in such deposits in most cases have a subvertical orientation, which is caused by the predominance of vertical stresses in rocks over horizontal ones. To determine the azimuthal direction of fractures, one can use, in particular, the dependence of the reflection coefficients of elastic waves on the boundaries with such media on the azimuth. This paper presents the results of physical modelling, demonstrating this dependence. To conduct experiments, we developed a technology for manufacturing models of azimuthally anisotropic (HTI) media with a high degree of anisotropy by 3-D printing. The features of the reflection of compression waves from the boundary of water and low-velocity azimuthally anisotropic media were experimentally investigated on the example of the model HTI medium produced by this method. Experiments have shown that at angles of incidence less than 25°, the reflection coefficients are practically independent from the azimuth. However, at larger angles of incidence, an azimuthal dependence of the reflection coefficients is observed, most pronounced at azimuths from 45° to 75°. The results of measurements in the direction of the isotropy plane agree well with the theoretical reflection coefficients for the boundary of isotropic media.

Reflection and Transmission of Elastic Waves by a Periodic Array of Cracks

1985 ◽  
Vol 52 (1) ◽  
pp. 33-41 ◽  
Author(s):  
Y. C. Angel ◽  
J. D. Achenbach
Keyword(s):  
Elastic Waves ◽  
Mixed Boundary ◽  
Body Wave ◽  
Normal Incidence ◽  
Reflection Coefficients ◽  
Reflection And Transmission ◽  
Low Frequencies ◽  
Finite Fourier Transform ◽  
Planar Array ◽  
Good Agreement

The interaction of elastic waves with a planar array of periodically spaced cracks of equal length is investigated. For normal incidence, reflection and transmission of longitudinal and transverse wave has been considered. Application of finite Fourier transform techniques reduces the solution of the mixed-boundary value problem for a typical strip to that of a singular integral equation. The solution has been obtained numerically. The reflected and transmitted far-field displacements are shown to be superpositions of a finite number of propagating body-wave modes. The numerical results have been checked by an application of the balance of rates of energies. The reflection coefficients have been plotted versus both the frequency and the ratio of crack length to crack spacing. The results according to exact elastodynamic theory have been compared with two approximations. Good agreement is observed at low frequencies.

Numerical Simulation of Compressive Residual Strength for Damaged Composite Laminates

2012 ◽  
Vol 525-526 ◽  
pp. 385-388
Author(s):  
Tian Jiao Qu ◽  
Xi Tao Zheng ◽  
Di Zhang
Keyword(s):  
Composite Laminates ◽  
Impact Test ◽  
Compressive Load ◽  
Low Velocity Impact ◽  
Fiber Breakage ◽  
Low Velocity ◽  
Appearance Time ◽  
Finite Element Software ◽  
Set Up ◽  
Good Agreement

After the low-velocity impact test of composite laminates of T800/BA9916, CAI test and compression test of laminates with a hole have been carried out. Two types of models were set up by the finite element software ABAQUS respectively. The FEA results were good agreement with the testing results. The investigation of models with a hole indicates that the appearance time of ultimate compressive load is earlier than that of fiber breakage expanding to boundary. Moreover, the diameter and the depth of blind hole significantly influence the ultimate compressive load.

scholarly journals Propagation of Transient Elastic Waves in Stratified Anisotropic Medium

1989 ◽  
Vol 56 (1) ◽  
pp. 235-235
Author(s):  
J. H. M. T. Van der Hijden ◽  
S. K. Datta
Keyword(s):  
Anisotropic Medium ◽  
Elastic Waves

Long‐wave elastic anisotropy in transversely isotropic media

Geophysics ◽  
1979 ◽  
Vol 44 (5) ◽  
pp. 896-917 ◽  
Author(s):  
James G. Berryman
Keyword(s):  
Elastic Anisotropy ◽  
Transversely Isotropic ◽  
Layered Media ◽  
Seismic Signal ◽  
Perturbation Scheme ◽  
Low Velocity ◽  
Compressional Waves ◽  
Long Wave ◽  
Transversely Isotropic Media ◽  
Isotropic Media

Compressional waves in horizontally layered media exhibit very weak long‐wave anisotropy for short offset seismic data within the physically relevant range of parameters. Shear waves have much stronger anisotropic behavior. Our results generalize the analogous results of Krey and Helbig (1956) in several respects: (1) The inequality [Formula: see text] derived by Postma (1955) for periodic isotropic, two‐layered media is shown to be valid for any homogeneous, transversely isotropic medium; (2) a general perturbation scheme for analyzing the angular dependence of the phase velocity is formulated and readily yields Krey and Helbig’s results in limiting cases; and (3) the effects of relaxing the assumption of constant Poisson’s ratio σ are considered. The phase and group velocities for all three modes of elastic wave propagation are illustrated for typical layered media with (1) one‐quarter limestone and three‐quarters sandstone, (2) half‐limestone and half‐sandstone, and (3) three‐quarters limestone and one‐quarter sandstone. It is concluded that anisotropic effects are greatest in areas where the layering is quite thin (10–50 ft), so that the wavelengths of the seismic signal are greater than the layer thickness and the layers are of alternately high‐ and low‐velocity materials.

The minimal flow unit in near-wall turbulence

1991 ◽  
Vol 225 ◽  
pp. 213-240 ◽  
Author(s):  
Javier Jiménez ◽  
Parviz Moin
Keyword(s):  
Wall Stress ◽  
Wall Layer ◽  
Flow Unit ◽  
Wall Turbulence ◽  
Longitudinal Vortex ◽  
Spanwise Direction ◽  
Wall Region ◽  
Low Velocity ◽  
Good Agreement ◽  
Near Wall

Direct numerical simulations of unsteady channel flow were performed at low to moderate Reynolds numbers on computational boxes chosen small enough so that the flow consists of a doubly periodic (in x and z) array of identical structures. The goal is to isolate the basic flow unit, to study its morphology and dynamics, and to evaluate its contribution to turbulence in fully developed channels. For boxes wider than approximately 100 wall units in the spanwise direction, the flow is turbulent and the low-order turbulence statistics are in good agreement with experiments in the near-wall region. For a narrow range of widths below that threshold, the flow near only one wall remains turbulent, but its statistics are still in fairly good agreement with experimental data when scaled with the local wall stress. For narrower boxes only laminar solutions are found. In all cases, the elementary box contains a single low-velocity streak, consisting of a longitudinal strip on which a thin layer of spanwise vorticity is lifted away from the wall. A fundamental period of intermittency for the regeneration of turbulence is identified, and that process is observed to consist of the wrapping of the wall-layer vorticity around a single inclined longitudinal vortex.

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