How to estimate the Green’s function of a heterogeneous medium between two passive sensors? Application to acoustic waves

2003 ◽  
Vol 83 (15) ◽  
pp. 3054-3056 ◽  
Author(s):  
Arnaud Derode ◽  
Eric Larose ◽  
Michel Campillo ◽  
Mathias Fink
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Acoustic Waves ◽  
Heterogeneous Medium ◽  
Passive Sensors

The Green’s function for surface acoustic waves: Comparison between theory and experiment

1996 ◽  
Vol 100 (3) ◽  
pp. 1538-1541 ◽  
Author(s):  
A. Mourad ◽  
C. Desmet ◽  
W. Lauriks ◽  
H. Coufal ◽  
J. Thoen
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Acoustic Waves ◽  
Surface Acoustic Waves ◽  
Theory And Experiment

scholarly journals Patched Green's function method applied to acoustic wave propagation in disordered media: an interdisciplinary approach

2020 ◽  
Vol 17 (5) ◽  
pp. 914-922
Author(s):  
Francisco A Moura ◽  
Wagner A Barbosa ◽  
Edwin F Duarte ◽  
Danyelle P Silva ◽  
Mauro S Ferreira ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Green’S Function ◽  
Green's Function ◽  
Acoustic Waves ◽  
Structural Information ◽  
Computational Cost ◽  
Computational Time ◽  
Model Parameters ◽  
Large Matrix

Abstract Modern visualization can be formulated as inversion problems that aim to obtain structural information about a complex medium through wave excitations. However, without numerically efficient forward calculations, even state-of-the-art inversion procedures are too computationally intensive to implement. We adapt a method previously used to treat transport in electronic waveguides to describe acoustic wave motion in complex media with high gains in computational time. The method consists of describing the system as if it was made of disconnected parts that are patched together. By expressing the system in this manner, wave-propagation calculations that otherwise would involve a very large matrix can be done with considerably smaller matrices instead. In particular, by treating one of such patches as a target whose parameters are changeable, we are able to implement target-oriented optimization in which the model parameters can be continuously refined until the ideal result is reproduced. The so-called Patched Green's function (PGF) approach is mathematically exact and involves no approximations, thus improving the computational cost without compromising accuracy. Given the generality of our method, it can be applied to a wide variety of inversion problems. Here we apply it to the case of seismic modeling where acoustic waves are used to map the earth subsurface in order to identify and explore mineral resources. The technique is tested with realistic seismic models and compared to standard calculation methods. The reduction in computational complexity is remarkable and paves the way to treating larger systems with increasing accuracy levels.

Mean flow refraction effects on sound radiated from localized sources in a jet

1998 ◽  
Vol 370 ◽  
pp. 149-174 ◽  
Author(s):  
CHRISTOPHER K. W. TAM ◽  
LAURENT AURIAULT
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Acoustic Waves ◽  
Flow Direction ◽  
Jet Flow ◽  
Parallel Flow ◽  
Mean Flow ◽  
Flow Approximation ◽  
Radiated Sound ◽  
Localized Sources

It is well-known that sound generated by localized sources embedded in a jet undergoes refraction as the acoustic waves propagate through the jet mean flow. For isothermal or hot jets, the effect of refraction causes the deflection of the radiated sound waves away from the jet flow direction. This gives rise to a cone of silence around the jet axis where there is a significant reduction in the radiated sound intensity. In this work, the mean flow refraction problem is investigated through the use of the reciprocity principle. Instead of the direct source Green's function, the adjoint Green's function with the source and observation points interchanged is used to quantify the effect of mean flow on sound radiation. One advantage of the adjoint Green's function is that the Green's functions for all the source locations in the jet radiating to a given direction in the far field can be obtained in a single calculation. This provides great savings in computational effort. Another advantage of the adjoint Green's function is that there is no singularity in the jet flow so that the problem can be solved numerically with axial as well as radial mean flow gradients included in a fairly straightforward manner. Extensive numerical computations have been carried out for realistic jet flow profiles with and without exercising the locally parallel flow approximation. It is concluded that the locally parallel flow approximation is valid as long as the direction of radiation is outside the cone of silence.

scholarly journals Surface and interface acoustic waves in solid-fluid superlattices: Green’s function approach

2006 ◽  
Vol 74 (14) ◽  
Author(s):  
Y. El Hassouani ◽  
E. H. El Boudouti ◽  
B. Djafari-Rouhani ◽  
H. Aynaou ◽  
L. Dobrzynski
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Acoustic Waves ◽  
Function Approach ◽  
Surface And Interface

GREEN'S FUNCTION MATCHING METHOD FOR REALISTIC CALCULATIONS OF INTERFACES

1985 ◽  
Vol 46 (C4) ◽  
pp. C4-321-C4-329 ◽  
Author(s):  
E. Molinari ◽  
G. B. Bachelet ◽  
M. Altarelli
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Matching Method

THE ATOMISTIC GREEN'S FUNCTION METHOD FOR INTERFACIAL PHONON TRANSPORT

2014 ◽  
Vol 17 (N/A) ◽  
pp. 89-145 ◽  
Author(s):  
Sridhar Sadasivam ◽  
Yuhang Che ◽  
Zhen Huang ◽  
Liang Chen ◽  
Satish Kumar ◽  
...  
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Function Method ◽  
Phonon Transport ◽  
Green’S Function Method
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