Sökning: "preconditioner"

Visar resultat 1 - 5 av 27 avhandlingar innehållade ordet preconditioner.

  1. 1. Multigrid Preconditioners for the Discontinuous Galerkin Spectral Element Method : Construction and Analysis

    Författare :Lea Miko Versbach; Numerisk analys; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Discontinuous Galerkin Method; Finite Volume Method; Implicit Schemes; Local Fourier Analysis; Multigrid Method; Preconditioner; Space-Time Discretization; Spectral Element Method;

    Sammanfattning : Discontinuous Galerkin (DG) methods offer a great potential for simulations of turbulent and wall bounded flows with complex geometries since these high-order schemes offer a great potential in handling eddies. Recently, space-time DG methods have become more popular. LÄS MER

  3. 2. Efficient Solvers for Space-Time Discontinuous Galerkin Spectral Element Methods

    Författare :Lea Miko Versbach; Numerisk analys; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Discontinuous Galerkin Method; Spectral Element Method; Finite Volume Method; Implicit Schemes; Preconditioner; Multigrid Method; Space-Time; Lobatto IIIC Method; Local Fourier Analysis;

    Sammanfattning : In this thesis we study efficient solvers for space-time discontinuous Galerkin spectral element methods (DG-SEM). These discretizations result in fully implicit schemes of variable order in both spatial and temporal directions. LÄS MER

  4. 3. Numerical Computations with Fundamental Solutions

    Författare :Per Sundqvist; Henrik Brandén; Sverker Holmgren; Alison Ramage; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; fundamental solution; partial differential equation; partial difference equation; iterative method; preconditioner; boundary method; Numerical Analysis; Numerisk analys;

    Sammanfattning : Two solution strategies for large, sparse, and structured algebraic systems of equations are considered. The first strategy is to construct efficient preconditioners for iterative solvers. The second is to reduce the sparse algebraic system to a smaller, dense system of equations, which are called the boundary summation equations. LÄS MER

  5. 4. 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

  7. 5. Studies on instability and optimal forcing of incompressible flows

    Författare :Mattias Brynjell-Rahkola; Dan S. Henningson; Ardeshir Hanifi; Philipp Schlatter; François Gallaire; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; hydrodynamic stability; optimal forcing; resolvent operator; Laplace preconditioner; spectral element method; eigenvalue problems; inverse power method; direct numerical simulations; Falkner–Skan–Cooke boundary layer; localized roughness; crossflow vortices; Blasius boundary layer; localized suction; helical vortices; lid-driven cavity; cylinder flow; Teknisk mekanik; Engineering Mechanics;

    Sammanfattning : This thesis considers the hydrodynamic instability and optimal forcing of a number of incompressible flow cases. In the first part, the instabilities of three problems that are of great interest in energy and aerospace applications are studied, namely a Blasius boundary layer subject to localized wall-suction, a Falkner–Skan–Cooke boundary layer with a localized surface roughness, and a pair of helical vortices. LÄS MER