Sökning: "Schur complement approximation"

Visar resultat 1 - 5 av 7 avhandlingar innehållade orden Schur complement approximation.

  1. 1. Analysis and Implementation of Preconditioners for Prestressed Elasticity Problems : Advances and Enhancements

    Författare :Ali Dorostkar; Maya Neytcheva; Thomas Huckle; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; FEM; Saddle point matrix; Preconditioning; Schur complement; Generalized Locally Toeplitz; Prestressed elasticity; Scientific Computing; Beräkningsvetenskap;

    Sammanfattning : In this work, prestressed elasticity problem as a model of the so-called glacial isostatic adjustment (GIA) process is studied. The model problem is described by a set of partial differential equations (PDE) and discretized with a mixed finite element (FE) formulation. LÄS MER

  3. 2. Robust Preconditioners Based on the Finite Element Framework

    Författare :Erik Bängtsson; Maya Neytcheva; Per Lötstedt; Svetozar Margenov; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; FEM; iterative solution method; algebraic multilevel preconditioner; sparse approximate inverse; block preconditioner; Schur complement approximation; nonsymmetric saddle point matrix; isostatic glacial adjustment; pre-stress advection; elasticity; viscoelasticity; in compressible solid; ABAQUS; BEM DDM; Scientific Computing; Beräkningsvetenskap;

    Sammanfattning : Robust preconditioners on block-triangular and block-factorized form for three types of linear systems of two-by-two block form are studied in this thesis. The first type of linear systems, which are dense, arise from a boundary element type of discretization of crack propagation problems. LÄS MER

  4. 3. Developments in preconditioned iterative methods with application to glacial isostatic adjustment models

    Författare :Ali Dorostkar; Maya Neytcheva; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Scientific Computing; Beräkningsvetenskap;

    Sammanfattning : This study examines the block lower-triangular preconditioner with element-wise Schur complement as the lower diagonal block applied on matrices arising from an application in geophysics. The element-wise Schur complement is a special approximation of the exact Schur complement that can be constructed in the finite element framework. LÄS MER

  5. 4. Implementation of the spectral element method and iterative solution techniques for 3D controlled-source electromagnetic modelling

    Författare :Michael Weiss; Thomas Kalscheuer; Michael Becken; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Controlled source electromagnetis; Electromagnetic theory; Numerical modelling; Applied geophysics; Geo-Electromagnetics; Spectral element method; Iterative solution methods; Preconditioning;

    Sammanfattning : Controlled-source electromagnetic methods are imaging techniques applied at/on the surface of the Earth which record the electromagnetic field in order to assess the electrical conductivity distribution of the Earth’s subsurface, along with anomalies in this material property, as well as to characterise and interpret structures in Earth’s crust. Extracting information from the recorded electromagnetic data requires inverse modelling algorithms. LÄS MER

  7. 5. Robust preconditioning methods for algebraic problems, arising in multi-phase flow models

    Författare :Xin He; Maya Neytcheva; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Scientific Computing; Beräkningsvetenskap;

    Sammanfattning : The aim of the project is to construct, analyse and implement fast and reliable numerical solution methods to simulate multi-phase flow, modeled by a coupled system consisting of the time-dependent Cahn-Hilliard and incompressible Navier-Stokes equations with variable viscosity and variable density. This thesis mainly discusses the efficient solution methods for the latter equations aiming at constructing preconditioners, which are numerically and computationally efficient, and robust with respect to various problem, discretization and method parameters. LÄS MER