Sökning: "MATHEMATICS Applied mathematics Numerical analysis"

Visar resultat 11 - 15 av 104 avhandlingar innehållade orden MATHEMATICS Applied mathematics Numerical analysis.

1. 11. 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

3. 12. Adaptive Algorithms and High Order Stabilization for Finite Element Computation of Turbulent Compressible Flow

   Författare :Murtazo Nazarov; Johan Hoffman; Timothy J. Barth; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Compressible flow; adaptivity; finite element method; a posteriori error estimates; Implicit LES; Applied mathematics; Tillämpad matematik; Numerical analysis; Numerisk analys;

   Sammanfattning : This work develops finite element methods with high order stabilization, and robust and efficient adaptive algorithms for Large Eddy Simulation of turbulent compressible flows. The equations are approximated by continuous piecewise linear functions in space, and the time discretization is done in implicit/explicit fashion: the second order Crank-Nicholson method and third/fourth order explicit Runge-Kutta methods. LÄS MER

4. 13. Stable High-Order Finite Difference Methods for Aerodynamics

   Författare :Magnus Svärd; Jan Nordström; Thomas Hagstrom; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; finite difference methods; high-order accuracy; summation-by-parts; stability; energy estimates; finite volume methods; Numerical analysis; Numerisk analys; Scientific Computing; Beräkningsvetenskap; Numerical Analysis;

   Sammanfattning : In this thesis, the numerical solution of time-dependent partial differential equations (PDE) is studied. In particular high-order finite difference methods on Summation-by-parts (SBP) form are analysed and applied to model problems as well as the PDEs governing aerodynamics. LÄS MER

5. 14. Runge–Kutta Time Step Selection for Flow Problems

   Författare :Karl Hörnell; Per Lötstedt; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Runge-Kutta; stepsize selection; optimization; flow problems; numerical analysis; Numerical Analysis; Numerisk analys;

   Sammanfattning : Optimality is studied for Runge-Kutta iteration for solving steady-state and time dependent flow problems. For the former type an algorithm for determining locally optimal time steps is developed, based on the fact that the squared norm of the residual produced by an m-stage scheme is a 2m-degree polynomial, the coefficients of which can be computed from scalar products of Krylov subspace vectors. LÄS MER

7. 15. Numerical methods for Sylvester-type matrix equations and nonlinear eigenvalue problems

   Författare :Emil Ringh; Elias Jarlebring; Johan Karlsson; Per Enqvist; Daniel Kressner; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Matrix equations; Lyapunov equation; Sylvester equation; nonlinear eigenvalue problems; two-parameter eigenvalue problems; Krylov methods; iterative methods; preconditioning; projection methods; Matrisekvationer; Lyapunovekvationen; Sylvesterekvationen; ickelinjära egenvärdesproblem; två-parameters egenvärdesproblem; Krylovmetoder; iterativa metoder; förkonditionering; projektionsmetoder; Tillämpad matematik och beräkningsmatematik; Applied and Computational Mathematics; Optimization and Systems Theory; Optimeringslära och systemteori; Numerical Analysis; Numerisk analys;

   Sammanfattning : Linear matrix equations and nonlinear eigenvalue problems (NEP) appear in a wide variety of applications in science and engineering. Important special cases of the former are the Lyapunov equation, the Sylvester equation, and their respective generalizations. These appear, e.g. LÄS MER