Search for dissertations about: "Fourier method"

Showing result 1 - 5 of 185 swedish dissertations containing the words Fourier method.

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

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

   Abstract : 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. READ MORE

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

   Author : Lea Miko Versbach; Numerisk analys; []
   Keywords : 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;

   Abstract : 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. READ MORE

5. 3. Potential Flow Panel Methods for the Calculation of Free-surface Flows with Lift

   Author : Carl-Erik Janson; Chalmers University of Technology; []
   Keywords : desingularized; shape optimization; Rankine source; waves; OCTOPUS; dipole; MMA; Dawson operator; boundary layer; vortex; Method of Moving Asymptotes; nonlinear; sailing yacht; four point operator; surface piercing wing; Navier-Stokes; numerical method; lift force; raised panel method; discrete Fourier transform; collocation point shift; potential flow; CFD; free surface; induced drag; SHIPFLOW; dispersion; damping; analytical method; hydrofoil;

   Abstract : Two non-linear Rankine-source panel methods are developed and implemented in the same computer code. The first method uses a four-point upwind operator on the free-surface to compute the velocity derivatives and to enforce the radiation condition while the second method uses an analytical expression for the velocity derivatives and a collocation point shift one panel upstream to prevent upstream waves. READ MORE

6. 4. Numerical Conformal Mappings for Waveguides

   Author : Anders Andersson; Börje Nilsson; Joachim Toft; Michael Benedicks; Växjö universitet; []
   Keywords : NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; waveguide; building block method; numerical conformal mappings; Schwarz–Christoffel mapping; rounded corners method; approximate curve factors; outer polygon method; boundary curvature; zipper method; geodesic algorithm; acoustic wave scattering; electro-magnetic wave scattering; Applied mathematics; Tillämpad matematik; Mathematics; Matematik; waveguides;

   Abstract : Acoustic or electro-magnetic scattering in a waveguide with varying direction and cross-section can be re-formulated as a two-dimensional scattering problem, provided that the variations take place in only one dimension at a time. By using the so-called Building Block Method, it is possible to construct the scattering properties of a combination of scatterers when the properties of each scatterer are known. READ MORE

7. 5. Optical Frequency Comb Fourier Transform Spectroscopy

   Author : Alexandra C. Johansson; Aleksandra Foltynowicz; Ove Axner; Jürgen Röpcke; Umeå universitet; []
   Keywords : NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Optical frequency comb spectroscopy; Fourier transform; molecular absorption dispersion; fysik; Physics;

   Abstract : Fourier transform spectroscopy (FTS) based on optical frequency combs is an excellent spectroscopic tool as it provides broadband molecular spectra with high spectral resolution and an absolutely calibrated frequency scale. Moreover, the equidistant comb mode structure enables efficient coupling of the comb to enhancement cavities, yielding high detection sensitivity. READ MORE