scholarly journals Inverse acoustic scattering problem in half-space with anisotropic random impedance

2017 ◽  
Vol 262 (4) ◽  
pp. 3139-3168 ◽  
Author(s):  
Tapio Helin ◽  
Matti Lassas ◽  
Lassi Päivärinta
Keyword(s):  
Half Space ◽  
Scattering Problem ◽  
Acoustic Scattering

Acoustic Scattering Cross Sections of Smart Obstacles: A Case Study

2011 ◽  
Vol 10 (3) ◽  
pp. 672-694
Author(s):  
Lorella Fatone ◽  
Maria Cristina Recchioni ◽  
Francesco Zirilli
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Space Shuttle ◽  
Scattering Problem ◽  
Plane Waves ◽  
Acoustic Scattering ◽  
Scattering Cross Section ◽  
Scattering Cross ◽  
Scattering Cross Sections

AbstractAcoustic scattering cross sections of smart furtive obstacles are studied and discussed. A smart furtive obstacle is an obstacle that, when hit by an incoming field, avoids detection through the use of a pressure current acting on its boundary. A highly parallelizable algorithm for computing the acoustic scattering cross section of smart obstacles is developed. As a case study, this algorithm is applied to the (acoustic) scattering cross section of a “smart” (furtive) simplified version of the NASA space shuttle when hit by incoming time-harmonic plane waves, the wavelengths of which are small compared to the characteristic dimensions of the shuttle. The solution to this numerically challenging scattering problem requires the solution of systems of linear equations with many unknowns and equations. Due to the sparsity of these systems of equations, they can be stored and solved using affordable computing resources. A cross section analysis of the simplified NASA space shuttle highlights three findings: i) the smart furtive obstacle reduces the magnitude of its cross section compared to the cross section of a corresponding “passive” obstacle; ii) several wave propagation directions fail to satisfactorily respond to the smart strategy of the obstacle; iii) satisfactory furtive effects along all directions may only be obtained by using a pressure current of considerable magnitude. Numerical experiments and virtual reality applications can be found at the website: http://www.ceri.uniromal.it/ceri/zirilli/w7.

scholarly journals Buried Object Detection by an Inexact Newton Method Applied to Nonlinear Inverse Scattering

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Matteo Pastorino ◽  
Andrea Randazzo
Keyword(s):  
Numerical Simulations ◽  
Half Space ◽  
Inverse Scattering ◽  
Scattering Problem ◽  
Inverse Scattering Problem ◽  
Continuous Model ◽  
Inexact Newton Method ◽  
Buried Objects ◽  
Buried Object ◽  
Full Nonlinearity

An approach to reconstruct buried objects is proposed. It is based on the integral equations of the electromagnetic inverse scattering problem, written in terms of the Green’s function for half-space geometries. The full nonlinearity of the problem is exploited in order to inspect strong scatterers. After discretization of the continuous model, the resulting equations are solved in a regularization sense by means of a two-step inexact Newton algorithm. The capabilities and limitations of the method are evaluated by means of some numerical simulations.

Acoustic Scattering by a Fluid-Encapsulating Spherical Viscoelastic Membrane Including Thermoviscous Effects

2005 ◽  
Vol 21 (4) ◽  
pp. 205-215 ◽  
Author(s):  
Seyyed M. Hasheminejad
Keyword(s):  
Viscoelastic Material ◽  
Viscoelastic Properties ◽  
Scattering Problem ◽  
Acoustic Scattering ◽  
Closed Form Solution ◽  
Practical Interest ◽  
Directivity Pattern ◽  
Form Solution ◽  
Heat Conducting ◽  
Harmonic Field

AbstractThis study provides a general analysis for scattering of a planar monochromatic compressional sound wave by a fluid-filled viscoelastic spherical membrane immersed in an unbounded viscous heat-conducting compressible fluid. The thermoviscous effects in the fluid are incorporated by application of a thin boundary layer model. The dynamic viscoelastic properties of the spherical membrane are rigorously taken into account in the solution of the acoustic-scattering problem. Havriliak-Negami model for viscoelastic material behaviour along with the appropriate wave-harmonic field expansions and the pertinent boundary conditions are employed to develop a closed-form solution in form of infinite series. Subsequently, the basic acoustic quantities, such as the scattered far-field pressure directivity pattern, and the scattering cross section are evaluated for given sets of viscoelastic material properties. Numerical results clearly indicate that, in addition to the traditional fluid thermoviscosity-related mechanisms, dynamic viscoelastic properties of the obstacle can be of significance in sound scattering. The presented analysis is of practical interest in development of contrast agents for echocardiographic research with potential clinical applications.

Fast Frequency-Domain Forward and Inverse Methods for Acoustic Scattering from Inhomogeneous Objects in Layered Media

2016 ◽  
Vol 24 (03) ◽  
pp. 1650008 ◽  
Author(s):  
Jing He Li ◽  
Qing Huo Liu
Keyword(s):  
Inverse Scattering ◽  
Large Scale ◽  
Layered Medium ◽  
Scattering Problem ◽  
Acoustic Scattering ◽  
Layered Media ◽  
Source Inversion ◽  
Multiple Frequency ◽  
Stable Convergence ◽  
Forward Solution

The fast scattering and inverse scattering algorithms for acoustic wave propagation and scattering in a layered medium with buried objects are an important research topic, especially for large-scale geophysical applications and for target detection. There have been increasing efforts in the development of practical, accurate, and efficient means of imaging subsurface target anomalies. In this work, the acoustic scattering problem in layered media is formulated as a volume integral equation and is solved by the stabilized bi-conjugate gradient fast Fourier transform (BCGS-FFT) method. By splitting the layered medium Green’s function interacting with the induced source into a convolution and a correlation, the acoustic fields can be calculated efficiently by the FFT algorithm. This allows both the forward solution and inverse solution to be computed with only [Formula: see text] computation time per iteration, where [Formula: see text] is the number of degrees of freedom. The inverse scattering is solved using a simultaneous multiple frequency contrast source inversion (CSI). The stable convergence of this inversion process makes the multiple frequency simultaneous CSI reconstruction practical for large acoustic problems. Some representative examples are shown to demonstrate the effectiveness of the forward and inverse solvers for acoustic applications.

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