Abstract

Quasi-Newton-type iterative solvers are developed for a wide class of nonlinear elliptic problems. The presented generalization of earlier efficient methods covers various nonuniformly elliptic problems arising, e.g., in non-Newtonian flows or for certain glaciology models. The robust estimates are reinforced by several examples.

The goal of this paper is to present various types of iterative solvers: gradient iteration, Newton’s method and a quasi-Newton method, for the finite element solution of elliptic problems arising in Gao type beam models (a geometrical type of nonlinearity, with respect to the Euler–Bernoulli hypothesis). Robust behaviour, i.e., convergence independently of the mesh parameters, is proved for these methods, and they are also tested with numerical experiments.

Variable preconditioning has earlier been developed as a realization of quasi-Newton methods for elliptic problems with uniformly bounded nonlinearities. This paper presents a generalization of this approach to strongly nonlinear problems, first on an operator level, then for elliptic problems allowing power order growth of nonlinearities. Numerical tests reinforce the convergence results.

We consider the numerical solution of elliptic problems in 3D with boundary nonlinearity, such as arising in stationary heat conduction models. We allow general non-orthotropic materials where the matrix of heat conductivities is a nondiagonal full matrix. The solution approach involves the finite element method (FEM) and Newton type iterations. We develop a quasi-Newton method for this problem, using spectral equivalence to approximate the derivatives. We derive the convergence of the method, and numerical experiments illustrate the robustness and the reduced computational cost.