Robust Multigrid Methods for Parameter Dependent Problems
- Joachim Schöberl (Johannes-Kepler-Universität Linz)
Abstract
Several models from computational mechanics lead to
parameter dependent problems of the form
with an elliptic operator A, an operator B with non-trivial
kernel, and a small, positive parameter
OM ALT="eps" SRC="1999_12_07_241_img2.gif">. We are
interested in the construction and analysis of robust multigrid
methods for the solution of the arising symmetric and positive
definite linear systems.
Specific examples considered in this talk are nearly incompressible
materials and the Reissner Mindlin plate model. We shortly present
robust non-conforming discretization schemes equivalent to
corresponding mixed finite element methods.
We will explain the necessary multigrid components, namely a block
smoother covering basis function of the kernel of B, and
prolongation operators mapping coarse-grid kernel functions to
fine-grid kernel functions.
We present the analysis for the two-level algorithm based on the
Additive Schwarz Technique. Optimal and robust convergence rates of
the multigrid W-cycle and variable V-cycle algorithms are proved by the
smoothing property and the approximation property. We have to use
norms depending in a proper way on the small parameter
T=10 ALIGN=BOTTOM ALT="eps" SRC="1999_12_07_241_img2.gif">.
Numerical experiments indicate also optimal convergence rates for
the V-cycle algorithm for both problems.