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Numerical solution of porous media flow with a dual-permeability model
Kváčová, Radka ; Dolejší, Vít (advisor) ; Congreve, Scott (referee)
The flow in porous media can be described by the Richards equation. However, porous media often exhibit a variety of heterogeneities, thus treat- ing a porous medium as homogeneous does not often fit the reality well. Therefore, we describe the flow in the porous medium using the Richards equation with the dual-permeability model, which assumes that the porous medium can be separated into two different media. This thesis is con- cerned with the numerical solution of the Richards equation with the dual- permeability model. We present the derivation of the dual-permeability model, and for the numerical solution, we use the space-time discontinu- ous Galerkin method. This produces a system of nonlinear algebraic equa- tions that need to be linearized. We perform a 1D experiment to verify the method and, finally, we present a 2D single-ring experiment to demonstrate the method. 1
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Parallel time integration for ordinary differential equations
Záboj, Petr ; Kučera, Václav (advisor) ; Dolejší, Vít (referee)
This thesis is about the problem of parallel-in-time integration methods. The main bulk of this thesis consists of the Parareal algorithm, which is one of the most widely used and studied parallel-in-time integration methods. We focus on the derivation of the Parareal algorithm using single-step integration methods and the multiple shoot- ing method. Finally, the properties of this algorithm are demonstrated with numerical experiments. 1
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Numerické řešení stlačitelného proudění
Prokopová, Jaroslava ; Feistauer, Miloslav (advisor) ; Dolejší, Vít (referee)
This work deals with the problem of inviscid, compressible flow in a time-dependent domain. We describe mathematical properties of the Euler equations and the system of governing equations is solved with the aid of the discontinuous Galerkin finite element method (DGFEM) in the time-indepentent domain. The main aim of this work is the study of this problem in time-dependent domains. For this reason the Arbitrary Lagrangian-Eulerian (ALE) method is presented. The governing equations are formulated in the ALE formulation and discretized in space and time by the DGFEM. Shortly we mention the shock capturing of the obtained scheme and the solution of the resulting linear system with the aid of Generalized Minimal Residual (GMRES) method. At the end of this work we present and compare results obtained by two different ALE formulations of the governing equations in the rectangular domain with a moving part of lower wall.
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Numerical solution of convection-diffusion equations using stabilization and adaptive methods
Lamač, Jan ; Knobloch, Petr (advisor) ; Dolejší, Vít (referee)
The subject of the present Master Thesis is a comparison of numerical solution of convection-diffusion equations aproaches using stabilization and adaptive methods. Firstly the basic aspects and thoughts of employed numerical method - Galerkin finite element method - are summarized. Consequently the most common kinds of stabilization methods for spurious oscillations diminishing are defined (esp. SUPG method). Next section is devoted to a posteriori error estimations and adaptive refinement of triangulation which could help to diminish the spurious oscillations too. All mentioned methods and techniques are implemented and finally tested on the sample examples.
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Mixed finite element method for the Poisson equation
Švihlová, Helena ; Knobloch, Petr (advisor) ; Dolejší, Vít (referee)
The aim of this bachelor thesis is the implementation of the mixed element method for the Poisson equation and the comparison with results of the classical finite element method. The thesis is divided into two chapters. In the first chapter there are descriptions of the spaces occurring in the weak formulation of the Poisson equation and descriptions of the spaces which are suitable to approach them. The second chapter studies the existence of the solutions of the approximated tasks and their convergence. The main part of this thesis are schemes of the solutions of both methods and the tables comparing errors of these solutions for three diferent functions. 1
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Interpolace hladkých funkcí pomocí kvadratických a kubických splinů
Eckstein, Jiří ; Kučera, Václav (advisor) ; Dolejší, Vít (referee)
In this thesis, we study properties of cubic and quadratic spline interpolation. First, we define the notions of spline and interpolation. We then merge them to study cubic and quadratic spline interpolations. We go through the individual spline interpolation types, show an algorithm for constructing selected types and sum up their basic properties. We then present a computer program based on the provided algorithms. We use it to construct spline interpolations of some sample functions and we calculate errors of these interpolation and compare them with theoretical estimates.
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A posteriori error estimates for numerical solution of convection-difusion problems
Šebestová, Ivana ; Dolejší, Vít (advisor) ; Sváček, Petr (referee) ; Brandts, Jan (referee)
This thesis is concerned with several issues of a posteriori error estimates for linear problems. In its first part error estimates for the heat conduction equation discretized by the backward Euler method in time and discontinuous Galerkin method in space are derived. In the second part guaranteed and locally efficient error estimates involving algebraic error for Poisson equation discretized by the discontinuous Galerkin method are derived. The technique is based on the flux reconstruction where meshes with hanging nodes and variable polynomial degree are allowed. An adaptive strategy combining both adaptive mesh refinement and stopping criteria for iterative algebraic solvers is proposed. In the last part a numerical method for computing guaranteed lower and upper bounds of principal eigenvalues of symmetric linear elliptic differential operators is presented. 1
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