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Parallel numeric solution of differential equations
Nečasová, Gabriela ; Čermák, Martin (referee) ; Kozek, Martin (referee) ; Šátek, Václav (advisor)
Diferenciální rovnice se studují již vice než 300 let. Poprvé parciální diferenciální rovnice použil švýcarský matematik a právník Nicolaus Bernoulli v 18. století. Parciální diferenciální rovnice druhého řádu se používají k modelování široké škály jevů ve vědě, technice a matematice, například šíření světelných a zvukových vln, pohybu tekutin a šíření tepla. Práce se zabývá paralelním numerickým řešením parciálních diferenciálních rovnic. Parciální diferenciální rovnice druhého řádu jsou pomocí metody přímek převedeny na rozsáhlé soustavy obyčejných diferenciálních rovnic. Prostorové derivace v parciální diferenciální rovnici jsou nahrazeny různými typy konečných diferencí. Výsledné soustavy obyčejných diferenciálních rovnic (problémy počátečních hodnot) jsou řešeny paralelně pomocí Runge-Kutta metod a nově navržené metody vyššího řádu založené na Taylorově řadě. Numerické experimenty vybraných problémů jsou realizovány na superpočítači s různým počtem výpočetních uzlů. Výsledky ukazují, že metoda založená na Taylorově řadě výrazně překonává standardní Runge-Kutta metody.
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Numerical analysis of approximation of nonpolygonal domains for discontinuous Galerkin method
Klouda, Filip ; Dolejší, Vít (advisor) ; Sobotíková, Veronika (referee)
Title: Numerical analysis of approximation of nonpolygonal domains for discon- tinuous Galerkin method Author: Filip Klouda Department: Department of Numerical Mathematics Supervisor: prof. RNDr. Vít Dolejší, Ph.D., DSc., KNM MFF UK Abstract: In this work we use the discontinuous Galerkin finite element method for the semidiscretization of a nonlinear nonstationary convection-diffusion pro- blem defined on a nonpolygonal two-dimensional domain. Using so called appro- ximating curved elements we define a piecewise polynomial approximation of the boundary of the domain and a space on which we search for a solution. We study the convergence of the method considering a symmetric as well as nonsymmetric discretization of diffusion terms and with the interior and boundary penalty. The obtained results allow us to derive an error estimate for the Discontinuous Galer- kin method employing the approximating curved elements. This estimate depends on the order of the approximation of the solution and also on the order of the approximation of the boundary. We describe one possibility of the construction of the approximating curved elements with the aid of a polynomial mapping given by an interpolation of points on the boundary. We present numerical experiments. Keywords: nonlinear convection-diffusion equation, discontinuous...
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Numerical analysis of approximation of nonpolygonal domains for discontinuous Galerkin method
Klouda, Filip ; Dolejší, Vít (advisor)
Title: Numerical analysis of approximation of nonpolygonal domains for discon- tinuous Galerkin method Author: Filip Klouda Department: Department of Numerical Mathematics Supervisor: prof. RNDr. Vít Dolejší, Ph.D., DSc., KNM MFF UK Abstract: In this work we use the discontinuous Galerkin finite element method for the semidiscretization of a nonlinear nonstationary convection-diffusion pro- blem defined on a nonpolygonal two-dimensional domain. Using so called appro- ximating curved elements we define a piecewise polynomial approximation of the boundary of the domain and a space on which we search for a solution. We study the convergence of the method considering a symmetric as well as nonsymmetric discretization of diffusion terms and with the interior and boundary penalty. The obtained results allow us to derive an error estimate for the Discontinuous Galer- kin method employing the approximating curved elements. This estimate depends on the order of the approximation of the solution and also on the order of the approximation of the boundary. We describe one possibility of the construction of the approximating curved elements with the aid of a polynomial mapping given by an interpolation of points on the boundary. We present numerical experiments. Keywords: nonlinear convection-diffusion equation, discontinuous...
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Numerical analysis of approximation of nonpolygonal domains for discontinuous Galerkin method
Klouda, Filip ; Dolejší, Vít (advisor)
Title: Numerical analysis of approximation of nonpolygonal domains for discon- tinuous Galerkin method Author: Filip Klouda Department: Department of Numerical Mathematics Supervisor: prof. RNDr. Vít Dolejší, Ph.D., DSc., KNM MFF UK Abstract: In this work we use the discontinuous Galerkin finite element method for the semidiscretization of a nonlinear nonstationary convection-diffusion pro- blem defined on a nonpolygonal two-dimensional domain. Using so called appro- ximating curved elements we define a piecewise polynomial approximation of the boundary of the domain and a space on which we search for a solution. We study the convergence of the method considering a symmetric as well as nonsymmetric discretization of diffusion terms and with the interior and boundary penalty. The obtained results allow us to derive an error estimate for the Discontinuous Galer- kin method employing the approximating curved elements. This estimate depends on the order of the approximation of the solution and also on the order of the approximation of the boundary. We describe one possibility of the construction of the approximating curved elements with the aid of a polynomial mapping given by an interpolation of points on the boundary. We present numerical experiments. Keywords: nonlinear convection-diffusion equation, discontinuous...
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Numerical analysis of approximation of nonpolygonal domains for discontinuous Galerkin method
Klouda, Filip ; Dolejší, Vít (advisor) ; Sobotíková, Veronika (referee)
Title: Numerical analysis of approximation of nonpolygonal domains for discon- tinuous Galerkin method Author: Filip Klouda Department: Department of Numerical Mathematics Supervisor: prof. RNDr. Vít Dolejší, Ph.D., DSc., KNM MFF UK Abstract: In this work we use the discontinuous Galerkin finite element method for the semidiscretization of a nonlinear nonstationary convection-diffusion pro- blem defined on a nonpolygonal two-dimensional domain. Using so called appro- ximating curved elements we define a piecewise polynomial approximation of the boundary of the domain and a space on which we search for a solution. We study the convergence of the method considering a symmetric as well as nonsymmetric discretization of diffusion terms and with the interior and boundary penalty. The obtained results allow us to derive an error estimate for the Discontinuous Galer- kin method employing the approximating curved elements. This estimate depends on the order of the approximation of the solution and also on the order of the approximation of the boundary. We describe one possibility of the construction of the approximating curved elements with the aid of a polynomial mapping given by an interpolation of points on the boundary. We present numerical experiments. Keywords: nonlinear convection-diffusion equation, discontinuous...
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Aplikace metody přímek na úlohy proudění
Segeth, Karel ; Šolín, P.
According to the general framework of the method of lines, we split the numerical solution of the nonstationary compressible Euler equations in 1D, 2D and 3D into the three following steps: First, the system of PDE´s is semidiscretized in space. Second the smoothness and Lipschitz continuity of the right-hand-side (RHS) of the arising system of ordinary equations (ODE´s) is analyzed and its solvability is discussed. Third, classical ODE packages ( we use ODEPACK and DDASPK ) are applied to the system of ODE´s.
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