We develop a parallel computational algorithm for simulating models of gel dynamics where the gel is described by two phases, a networked polymer and a fluid solvent. The models consist of transport equations for the two phases, two coupled momentum equations, and a volumeaveraged incompressibility constraint. Multigrid with Vanka-type box relaxation scheme is used as preconditioner for the Kry...

We describe the structure of a fast solver for the Helmholtz equation in the optimized Schwarz framework, based on a preconditioner that leverages impedance-matching boundary conditions on subdomains. In the case of a simple 2D waveguide numerical example, the method requires no more than 4 GMRES iterations, independently of the frequency and the number of subdomains. The challenge remains to m...

The Progressive GMRES algorithm, introduced by Beckermann and Reichel in 2008, is a residual-minimizing short-recurrence Krylov subspace method for solving a linear system in which the coefficient matrix has a low-rank skew-Hermitian part. We analyze this algorithm, observing a critical instability that makes the method unsuitable for some problems. To work around this issue we introduce a diff...

Abstract Generalized eigenvalue problems on the overlap(GenEO) is a method for computing an operator-dependent spectral coarse space to be combined with local solves subdomains form robust parallel domain decomposition preconditioner elliptic PDEs. It has previously been proved, in self-adjoint and positive-definite case, that this method, when used as conjugate gradients, yields iteration numb...

The present paper intends to couple the Fast Multipole Method (FMM) with the Boundary Element Method (BEM) in 2D acoustic problems. The evaluation of the integrals involved in the governing Boundary Integral Equations (BIEs) is fasten by the FMM contribution. The multipole expansion and some suitable moment translations make the procedure much faster if compared to the conventional approach. Th...

This paper is devoted to a class of iterative methods for solving nonsymmetric or indeenite problems that are dominated by some SPD (symmetric positive deenite) problems. The algorithm is based on a direct solver for the original equation restricted on a small subspace and a given iterative method for the SPD equation. It is shown that any convergent iterative method for the SPD problem will gi...

This report describes a new family of Newton-Krylov methods for solving nonlinear systems of equations arising from the solution of Richards’ equation and in fully implicit formulations in air-water systems. The basic approach is to perform secant (Broyden) updates restricted to the Krylov subspace generated by the GMRES iterative solver. This approach is introduced as Krylov-secant methods. On...

An ill-posed Cauchy problem for a 3D elliptic PDE with variable coefficients is considered. A well-posed quasi-boundary-value (QBV) problem is given to approximate it. Some stability error estimates are given. For the numerical implementation, a large sparse system is obtained from the discretizing the QBV problem using finite difference method (FDM). A LeftPreconditioner Generalized Minimum Re...

We present a monolithic geometric multigrid solver for fluid-structure interaction problems in Arbitrary Lagrangian Eulerian coordinates. The coupled dynamics of an incompressible fluid with nonlinear hyperelastic solids gives rise to very large and ill conditioned systems of algebraic equations. Direct solvers usually are out of question due to memory limitations, standard coupled iterative so...