Sökning: "Helmholtz equation"

Visar resultat 1 - 5 av 43 avhandlingar innehållade orden Helmholtz equation.

  1. 1. Domain Decomposition and Preconditioned Iterative Methods for the Helmholtz Equation

    Författare :Elisabeth Larsson; Kurt Otto; Bengt Fornberg; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Helmholtz equation; domain decomposition; preconditioned iterative method; fast transforms; parallelization; Numerical Analysis; Numerisk analys;

    Sammanfattning : New preconditioned iterative solution methods for the Helmholtz equation are constructed. To evaluate the performance of the methods, two-dimensional problems with a waveguide geometry are used as model problems. Second- and fourth-order accurate finite difference discretizations are used. LÄS MER

  3. 2. A Fast Method for Solving the Helmholtz Equation Based on Wave Splitting

    Författare :Jelena Popovic; Olof Runborg; Elisabeth Larsson; KTH; []
    Nyckelord :Helmholtz equation; high fequency waves;

    Sammanfattning : In this thesis, we propose and analyze a fast method for computing the solution of the Helmholtz equation in a bounded domain with a variable wave speed function. The method is based on wave splitting. The Helmholtz equation is first split into one--way wave equations which are then solved iteratively for a given tolerance. LÄS MER

  4. 3. On adaptive finite element methods based on a posteriori estimates

    Författare :Axel Målqvist; Göteborgs universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; finite element method; Galerkin; duality; a posteriori error estimation; adaptivity; Poisson equation; boundary penalty method; Helmholtz equation; pollution; variational multiscale method; adaptivity;

    Sammanfattning : .... LÄS MER

  5. 4. Inverse Problems in Tomography and Fast Methods for Singular Convolutions

    Författare :Fredrik Andersson; Matematik LTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Mathematics; Matematik; Unequally spaced FFT; Integral transforms; Singular integrals; Lippmann?Schwinger equation; Helmholtz equation; Inverse problems; Fast Gauss transform; Fast summation; Convolution; Radon transform; Tomography;

    Sammanfattning : There are two, partially interlaced, themes treated in this thesis; inverse problems of tomographic type and fast and accurate methods for the application of convolution operators. Regarding the first theme, the inverse problem of Doppler tomography is considered and the Doppler moment transform is introduced for that purpose. LÄS MER

  7. 5. Material distribution-based topology optimization for wave propagation problems

    Författare :Ahmad Hasnain Bokhari; Eddie Wadbro; Martin Berggren; Roland Herzog; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; topology optimization; material distribution; wave propagation problems; Helmholtz equation; acoustics; electromagnetics; plasmonics;

    Sammanfattning : This thesis employs material distribution-based topology optimization for wave propagation problems. In the material distribution approach, we define a material indicator function that models the presence and absence of material in a design domain. LÄS MER