Discrete geometric homogenisation and inverse homogenisation of an elliptic operator

Citation

Donaldson, Roger David (2008) Discrete geometric homogenisation and inverse homogenisation of an elliptic operator. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-05212008-164705

Abstract

We show how to parameterise a homogenised conductivity in $R^2$ by a scalar function $s(x)$, despite the fact that the conductivity parameter in the related up-scaled elliptic operator is typically tensor valued. Ellipticity of the operator is equivalent to strict convexity of $s(x)$, and with consideration to mesh connectivity, this equivalence extends to discrete parameterisations over triangulated domains. We apply the parameterisation in three contexts: (i) sampling $s(x)$ produces a family of stiffness matrices representing the elliptic operator over a hierarchy of scales; (ii) the curvature of $s(x)$ directs the construction of meshes well-adapted to the anisotropy of the operator, improving the conditioning of the stiffness matrix and interpolation properties of the mesh; and (iii) using electric impedance tomography to reconstruct $s(x)$ recovers the up-scaled conductivity, which while anisotropic, is unique. Extensions of the parameterisation to $R^3$ are introduced.

Thesis Files