Modeling of low‐frequency Stoneley wave propagation in an irregular borehole

1994 ◽  
Author(s):  
Kazuhiko Tezuka ◽  
Chuen H. Cheng ◽  
Xiao Ming Tang
Keyword(s):  
Wave Propagation ◽  
Low Frequency ◽  
Stoneley Wave

Modeling of low‐frequency Stoneley‐wave propagation in an irregular borehole

Geophysics ◽  
1997 ◽  
Vol 62 (4) ◽  
pp. 1047-1058 ◽  
Author(s):  
Kazuhiko Tezuka ◽  
C. H. (Arthur) Cheng ◽  
X. M. Tang
Keyword(s):  
Wave Propagation ◽  
Finite Difference ◽  
Finite Difference Methods ◽  
Low Frequency ◽  
Field Application ◽  
Boundary Integral ◽  
Modeling Method ◽  
Stoneley Wave ◽  
Wave Interactions ◽  
Property Changes

A fast modeling method is formulated for low‐frequency Stoneley‐wave propagation in an irregular borehole. This fast modeling method provides synthetic waveforms which include the effects of two borehole irregularities, diameter changes (washout), and formation property changes. The essential physics of the low‐frequency Stoneley waves are captured with a simple 1-D model. A mass‐balance boundary condition and a propagator matrix are used to express Stoneley‐wave interactions with the borehole irregularities. The accuracy of the proposed method was confirmed through comparison with existing finite‐difference and boundary integral modeling methods that yielded cross‐correlations greater than 0.98. Comparison of synthetic records calculated for an actual borehole with field records showed qualitative agreement in the major reflections because of the washout zones, but showed some disagreements in the reflections caused by the fractures. Since the synthetic records include only information relating to the borehole geometry and the elastic properties of formation, the reflection caused by the fracture will appear only in the field record. These results suggest the possibility of distinguishing Stoneley‐wave reflections caused by fractures from those caused by borehole irregularities. Further, the fast computational speed of this method—over 300 times faster than either boundary integral or finite‐difference methods—makes it quite suitable for field application.

Numerical Simulation of the Buried Object Detection Based on Underwater Plasma Acoustic Source

2011 ◽  
Vol 105-107 ◽  
pp. 80-83
Author(s):  
Jun Zhang ◽  
Xin Wu Zeng ◽  
Yi Bo Wang ◽  
Zhen Fu Zhang ◽  
Dan Chen
Keyword(s):  
Wave Propagation ◽  
Object Detection ◽  
Pulse Length ◽  
Low Frequency ◽  
Basic Mechanism ◽  
Propagation Model ◽  
Staggered Grid ◽  
Acoustic Source ◽  
Buried Objects ◽  
Buried Object

Detection and classification of buried objects is of great importance in underwater counterterrorism and archaeology. To penetrate the sediment, a low frequency intensive acoustic source is needed. Underwater plasma acoustic source (UPAS) with high voltage discharge has the advantage of adjustable pulse length, high source level output and no pollution to the environment, which can satisfy these needs. In this paper, we introduced the UPAS, including its basic mechanism, structure and pressure output. Then we build up an elastic wave propagation model, solved it with finite difference and staggered grid methods, and combined with certain source and boundary condition, we simulated and analyzed the pressure wave propagation in time domain with an aluminum cylinder buried in sediment, from the results we validated the effectiveness of UPAS in the application of buried object detection.

scholarly journals Rossby Wave Ray Tracing in a Barotropic Divergent Atmosphere

2008 ◽  
Vol 65 (5) ◽  
pp. 1679-1691 ◽  
Author(s):  
Chungu Lu ◽  
John P. Boyd
Keyword(s):  
Wave Propagation ◽  
Ray Tracing ◽  
Rossby Wave ◽  
Level Structure ◽  
Low Frequency ◽  
Present Theory ◽  
Wave Ray ◽  
Divergent Wind ◽  
Rossby Wave Propagation ◽  
Upper Level

Abstract The effects of divergence on low-frequency Rossby wave propagation are examined by using the two-dimensional Wentzel–Kramers–Brillouin (WKB) method and ray tracing in the framework of a linear barotropic dynamic system. The WKB analysis shows that the divergent wind decreases Rossby wave frequency (for wave propagation northward in the Northern Hemisphere). Ray tracing shows that the divergent wind increases the zonal group velocity and thus accelerates the zonal propagation of Rossby waves. It also appears that divergence tends to feed energy into relatively high wavenumber waves, so that these waves can propagate farther downstream. The present theory also provides an estimate of a phase angle between the vorticity and divergence centers. In a fully developed Rossby wave, vorticity and divergence display a π/2 phase difference, which is consistent with the observed upper-level structure of a mature extratropical cyclone. It is shown that these theoretical results compare well with observations.

Characteristics of Band Gap and Low-frequency Wave Propagation of Mechanically Tunable Phononic Crystals with Scatterers in Periodic Porous Elastomeric Matrices

2021 ◽  
pp. 1-34
Author(s):  
Shaowu Ning ◽  
Dongyang Chu ◽  
Fengyuan Yang ◽  
Heng Jiang ◽  
Zhanli Liu ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Coupling Effect ◽  
Low Frequency ◽  
Phononic Crystals ◽  
Band Gaps ◽  
Dynamic Responses ◽  
Acoustic Metamaterials ◽  
Frequency Wave ◽  
Strong Coupling Effect ◽  
The Matrix

Abstract The characteristics of passive responses and fixed band gaps of phononic crystals (PnCs) limit their possible applications. For overcoming this shortcoming, a class of tunable PnCs comprised of multiple scatterers and soft periodic porous elastomeric matrices are designed to manipulate the band structures and directionality of wave propagation through the applied deformation. During deformation, some tunable factors such as the coupling effect of scatterer and hole in the matrix, geometric and material nonlinearities, and the rearrangement of scatterer are activated by deformation to tune the dynamic responses of PnCs. The roles of these tunable factors in the manipulation of dynamic responses of PnCs are investigated in detail. The numerical results indicate that the tunability of the dynamic characteristic of PnCs is the result of the comprehensive function of these tunable factors mentioned above. The strong coupling effect between the hole in the matrix and the scatterer contributes to the formation of band gaps. The geometric nonlinearity of matrix and rearrangement of scatterer induced by deformation can simultaneously tune the band gaps and the directionality of wave propagation. However, the matrix's material nonlinearity only adjusts the band gaps of PnCs and does not affect the directionality of wave propagation in them. The research extends our understanding of the formation mechanism of band gaps of PnCs and provides an excellent opportunity for the design of the optimized tunable PnCs and acoustic metamaterials.

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