Scattering of stationary waves from buried threedimensional inhomogeneities
Research output: Thesis › Doctoral Thesis (compilation)
Abstract
The Tmatrix method (also called the "extended boundary condition method" or "null field approach") is a formalism, which applies to scattering of linear classical waves (i.e. acoustic, electromagnetic and elastic waves). The object of this thesis is to extend the TMatrix formalism to a geometry consisting of two
halfspaces, one of which contains a threedimensional inhomogeneity. The two halfspaces, separated by an infinite Interface, are otherwise homogeneous, linear and isotropic. The source that excites the scatterer can be located in any of the halfspaces or inside the inhomogeneity, though explicit equations and numerical computations are presented only for sources outside the inhomogeneity (above or below the interface). The assumptions on the sources are fairly weak, and in the numerical computations we consider a monopole or dipole source or an incoming Rayleigh surface wave. Furthermore the formalism applies to a large class of inhomogeneities, and we illustrate some: a sphere, a spheroid (both oblate and prolate) and two spheres. The orientation of the obstacle is arbitrary both with respect to the surface and the source. The scattered field in the general formalism is in a natural way separated in two terms, one of which is the directly scattered field as if no buried inhomogeneity were present. The other term reflects the presence of the inhomogeneity and that is the one which has been the quantity of primary interest in the numerical computations.
halfspaces, one of which contains a threedimensional inhomogeneity. The two halfspaces, separated by an infinite Interface, are otherwise homogeneous, linear and isotropic. The source that excites the scatterer can be located in any of the halfspaces or inside the inhomogeneity, though explicit equations and numerical computations are presented only for sources outside the inhomogeneity (above or below the interface). The assumptions on the sources are fairly weak, and in the numerical computations we consider a monopole or dipole source or an incoming Rayleigh surface wave. Furthermore the formalism applies to a large class of inhomogeneities, and we illustrate some: a sphere, a spheroid (both oblate and prolate) and two spheres. The orientation of the obstacle is arbitrary both with respect to the surface and the source. The scattered field in the general formalism is in a natural way separated in two terms, one of which is the directly scattered field as if no buried inhomogeneity were present. The other term reflects the presence of the inhomogeneity and that is the one which has been the quantity of primary interest in the numerical computations.
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External organisations 

Research areas and keywords  Subject classification (UKÄ) – MANDATORY

Original language  English 

Qualification  Doctor 
Award date  1979 Nov 22 
Publication status  Published  1979 
Publication category  Research 
Externally published  Yes 
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