Calculation on Acoustic Scattering of Viscoelastic Layer Coupling with Elastic Shell

2012 ◽  
Vol 248 ◽  
pp. 107-113
Author(s):  
Zhong Kun Jin ◽  
Tong Qing Wang
Keyword(s):  
Boundary Condition ◽  
Spherical Shell ◽  
Elastic Shell ◽  
Acoustic Scattering ◽  
Impedance Boundary Condition ◽  
Target Strength ◽  
Viscoelastic Layer ◽  
Impedance Boundary ◽  
Elastic Spherical Shell ◽  
Element Method

This paper is devoted to numerical research on coupling between elastic spherical shell and the coated viscoelastic layer as well as the scattering of incident plane wave by the double-layer spherical shell. The scattering sound field is solved based on impedance boundary condition by boundary element method (BEM). Dynamic finite element method (FEM) is used to numerically simulate the acoustic impedance boundary condition which involved in the coupled spherical shell. Impedance distribution for elastic spherical shell and elastic spherical shell coated viscoelastic layer is calculated and its effect on the target strength (TS) is discussed finally.

A Study of Three-Dimensional Acoustic Scattering by Arbitrary Distribution Multibodies Using Extended Immersed Boundary Method

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Yongsong Jiang ◽  
Xiaoyu Wang ◽  
Xiaodong Jing ◽  
Xiaofeng Sun
Keyword(s):  
Boundary Condition ◽  
Computational Model ◽  
Acoustic Field ◽  
Three Dimensional ◽  
Acoustic Scattering ◽  
Impedance Boundary Condition ◽  
Immersed Boundary ◽  
Complex Geometries ◽  
Impedance Boundary ◽  
Wall Boundary Conditions

A three-dimensional computational model for acoustic scattering with complex geometries is presented, which employs the immersed boundary technique to deal with the effect of both hard and soft wall boundary conditions on the acoustic fields. In this numerical model, the acoustic field is solved on uniform Cartesian grids, together with simple triangle meshes to partition the immersed body surface. A direct force at the Lagrangian points is calculated from an influence matrix system, and then spreads to the neighboring Cartesian grid points to make the acoustic field satisfy the required boundary condition. This method applies a uniform stencil on the whole domain except at the computational boundary, which has the benefit of low dispersion and dissipation errors of the used scheme. The method has been used to simulate two benchmark problems to validate its effectiveness and good agreements with the analytical solutions are achieved. No matter how complex the geometries are, single body or multibodies, complex geometries do not pose any difficulty in this model. Furthermore, a simple implementation of time-domain impedance boundary condition is reported and demonstrates the versatility of the computational model.

scholarly journals The Mathematical Basis of the Inverse Scattering Problem for Cracks from Near-Field Data

2015 ◽  
Vol 2015 ◽  
pp. 1-8
Author(s):  
Yao Mao ◽  
Yongguang Chen ◽  
Jun Guo
Keyword(s):  
Boundary Condition ◽  
Inverse Scattering ◽  
Surface Impedance ◽  
Near Field ◽  
Scattering Problem ◽  
Acoustic Scattering ◽  
Inverse Scattering Problem ◽  
Impedance Boundary Condition ◽  
Mathematical Basis ◽  
Impedance Boundary

We consider the acoustic scattering problem from a crack which has Dirichlet boundary condition on one side and impedance boundary condition on the other side. The inverse scattering problem in this paper tries to determine the shape of the crack and the surface impedance coefficient from the near-field measurements of the scattered waves, while the source point is placed on a closed curve. We firstly establish a near-field operator and focus on the operator’s mathematical analysis. Secondly, we obtain a uniqueness theorem for the shape and surface impedance. Finally, by using the operator’s properties and modified linear sampling method, we reconstruct the shape and surface impedance.

A stable method for an inverse problem in acoustic scattering by an obstacle with an impedance boundary condition

1984 ◽  
Vol 98 (3-4) ◽  
pp. 355-364 ◽  
Author(s):  
Robert T. Smith
Keyword(s):  
Boundary Condition ◽  
Inverse Problem ◽  
Acoustic Waves ◽  
Acoustic Scattering ◽  
Two Dimensions ◽  
Impedance Boundary Condition ◽  
Compact Set ◽  
Stable Method ◽  
Low Frequencies ◽  
Impedance Boundary

SynopsisWe examine the case of plane, time-harmonic acoustic waves in two dimensions, scattered by an obstacle on the surface of which an impedance boundary condition is imposed. A stable method is developed for solving the inverse problem ofdetermining both the shape of the scatterer and the surface impedance from measurements of the asymptotic behaviour of the scattered waves at low frequencies. We accomplish this by minimizing an appropriate functional over a compact set of admissible boundary curves and admissible impedances.

scholarly journals Method of interior boundaries in a mixed problem of acoustic scattering

1999 ◽  
Vol 5 (2) ◽  
pp. 173-192 ◽  
Author(s):  
P. A. Krutitskii
Keyword(s):  
Boundary Condition ◽  
Mixed Problem ◽  
Dirichlet Boundary ◽  
Acoustic Scattering ◽  
Integral Equation Method ◽  
Boundary Integral ◽  
Impedance Boundary Condition ◽  
Impedance Boundary ◽  
Wave Numbers ◽  
Special Modification

The mixed problem for the Helmholtz equation in the exterior of several bodies (obstacles) is studied in 2 and 3 dimensions. The Dirichlet boundary condition is given on some obstacles and the impedance boundary condition is specified on the rest. The problem is investigated by a special modification of the boundary integral equation method. This modification can be called ‘Method of interior boundaries’, because additional boundaries are introduced inside scattering bodies, where impedance boundary condition is given. The solution of the problem is obtained in the form of potentials on the whole boundary. The density in the potentials satisfies the uniquely solvable Fredholm equation of the second kind and can be computed by standard codes. In fact our method holds for any positive wave numbers. The Neumann, Dirichlet, impedance problems and mixed Dirichlet–Neumann problem are particular cases of our problem.

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