Generation of ultrasonic finite-amplitude waves through a multiple scattering medium by time reversal in a waveguide

2017 ◽  
Vol 141 (5) ◽  
pp. 3739-3739
Author(s):  
Gonzalo A. Garay ◽  
Nicolás Benech ◽  
Carlos Negreira ◽  
Yamil Abraham
Keyword(s):  
Multiple Scattering ◽  
Time Reversal ◽  
Finite Amplitude ◽  
Scattering Medium ◽  
Finite Amplitude Waves

Modeling time‐reversal focusing in a multiple scattering medium

2008 ◽  
Vol 123 (5) ◽  
pp. 3341-3341
Author(s):  
Kevin J. Haworth ◽  
Jeffrey B. Fowlkes ◽  
Paul L. Carson ◽  
Oliver D. Kripfgans
Keyword(s):  
Multiple Scattering ◽  
Time Reversal ◽  
Scattering Medium

Acoustical imaging through a multiple scattering medium using a time-reversal mirror

2000 ◽  
Vol 107 (2) ◽  
pp. L7-L12 ◽  
Author(s):  
Philippe Roux ◽  
Arnaud Derode ◽  
Aymeric Peyre ◽  
Arnaud Tourin ◽  
Mathias Fink
Keyword(s):  
Multiple Scattering ◽  
Time Reversal ◽  
Scattering Medium ◽  
Acoustical Imaging ◽  
Time Reversal Mirror

scholarly journals Unified double- and single-sided homogeneous Green’s function representations

2016 ◽  
Vol 472 (2190) ◽  
pp. 20160162 ◽  
Author(s):  
Kees Wapenaar ◽  
Joost van der Neut ◽  
Evert Slob
Keyword(s):  
Green’S Function ◽  
Multiple Scattering ◽  
Green's Function ◽  
Time Reversal ◽  
Wave Theory ◽  
Boundary Integral ◽  
Open Boundary ◽  
Quantum Mechanical ◽  
Holographic Imaging ◽  
Scattering Time

In wave theory, the homogeneous Green’s function consists of the impulse response to a point source, minus its time-reversal. It can be represented by a closed boundary integral. In many practical situations, the closed boundary integral needs to be approximated by an open boundary integral because the medium of interest is often accessible from one side only. The inherent approximations are acceptable as long as the effects of multiple scattering are negligible. However, in case of strongly inhomogeneous media, the effects of multiple scattering can be severe. We derive double- and single-sided homogeneous Green’s function representations. The single-sided representation applies to situations where the medium can be accessed from one side only. It correctly handles multiple scattering. It employs a focusing function instead of the backward propagating Green’s function in the classical (double-sided) representation. When reflection measurements are available at the accessible boundary of the medium, the focusing function can be retrieved from these measurements. Throughout the paper, we use a unified notation which applies to acoustic, quantum-mechanical, electromagnetic and elastodynamic waves. We foresee many interesting applications of the unified single-sided homogeneous Green’s function representation in holographic imaging and inverse scattering, time-reversed wave field propagation and interferometric Green’s function retrieval.

scholarly journals Finite-amplitude steady waves in plane viscous shear flows

1985 ◽  
Vol 160 ◽  
pp. 281-295 ◽  
Author(s):  
F. A. Milinazzo ◽  
P. G. Saffman
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Stokes Equations ◽  
Reynolds Numbers ◽  
Finite Amplitude ◽  
Linear Instability ◽  
Navier Stokes ◽  
Unidirectional Flow ◽  
Viscous Shear ◽  
Finite Amplitude Waves

Computations of two-dimensional solutions of the Navier–Stokes equations are carried out for finite-amplitude waves on steady unidirectional flow. Several cases are considered. The numerical method employs pseudospectral techniques in the streamwise direction and finite differences on a stretched grid in the transverse direction, with matching to asymptotic solutions when unbounded. Earlier results for Poiseuille flow in a channel are re-obtained, except that attention is drawn to the dependence of the minimum Reynolds number on the physical constraint of constant flux or constant pressure gradient. Attempts to calculate waves in Couette flow by continuation in the velocity of a channel wall fail. The asymptotic suction boundary layer is shown to possess finite-amplitude waves at Reynolds numbers orders of magnitude less than the critical Reynolds number for linear instability. Waves in the Blasius boundary layer and unsteady Rayleigh profile are calculated by employing the artifice of adding a body force to cancel the spatial or temporal growth. The results are verified by comparison with perturbation analysis in the vicinity of the linear-instability critical Reynolds numbers.

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