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Numerical minimization of energy functionals in continuum mechanics using hp-FEM in MATLAB
Moskovka, Alexej ; Frost, Miroslav ; Valdman, Jan
Many processes in mechanics and thermodynamics can be formulated as a minimization of a particular energy functional. The finite element method can be used for an approximation of such functionals in a finite-dimensional subspace. Consequently, the numerical minimization methods (such as quasi-Newton and trust region) can be used to find a minimum of the functional. Vectorization techniques used for the evaluation of the energy together with the assembly of discrete energy gradient and Hessian sparsity are crucial for evaluation times. A particular model simulating the deformation of a Neo-Hookean solid body is solved in this contribution by minimizing the corresponding energy functional. We implement both P1 and rectangular hp-finite elements and compare their efficiency with respect to degrees of freedom and evaluation times.
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HP-FEM for Coupled Problems in Fluid Dynamics
Dubcová, Lenka
of dissertation hp-FEM FOR COUPLED PROBLEMS IN FLUID DYNAMICS Lenka Dubcová The thesis is concerned with the solution of multiphysics problems de- scribed by partial differential equations using higher-order finite element method (hp-FEM). Basics of hp-FEM are described, together with some practical details and challenges. The hp-adaptive strategy, based on the reference solution and meshes with arbitrary level hanging nodes, is dis- cussed. The thesis is mainly concerned with the extension of this strategy to monolithical solution of coupled multiphysics problems, where each physical field exhibits different qualitative behavior. In such problems, each physical field is discretized on an individual mesh automatically obtained by the adaptive algorithm to suit the best the corresponding so- lution component. Moreover, the meshes can change in time, following the needs of the solution components. All described methods and tech- nologies are demonstrated on several examples throughout the thesis, where comparisons with traditionally used approaches are shown.
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HP-FEM for Coupled Problems in Fluid Dynamics
Dubcová, Lenka
of dissertation hp-FEM FOR COUPLED PROBLEMS IN FLUID DYNAMICS Lenka Dubcová The thesis is concerned with the solution of multiphysics problems de- scribed by partial differential equations using higher-order finite element method (hp-FEM). Basics of hp-FEM are described, together with some practical details and challenges. The hp-adaptive strategy, based on the reference solution and meshes with arbitrary level hanging nodes, is dis- cussed. The thesis is mainly concerned with the extension of this strategy to monolithical solution of coupled multiphysics problems, where each physical field exhibits different qualitative behavior. In such problems, each physical field is discretized on an individual mesh automatically obtained by the adaptive algorithm to suit the best the corresponding so- lution component. Moreover, the meshes can change in time, following the needs of the solution components. All described methods and tech- nologies are demonstrated on several examples throughout the thesis, where comparisons with traditionally used approaches are shown.
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Řešení 3D elektrostatických problémů se singulaturou s použitím adaptivní hp-FEM
Kůs, Pavel ; Šolín, Pavel ; Doležel, Ivo
For most numerical methods, accurate resolution of singularities occurring at sharp re-entrant corners or edges of electrically conductive objects is highly problematic. Finite differences are known for their inability to treat complex geometries, and traditional low-order (piecewise-linear or quadratic) finite element methods (FEM) exhibit extremely poor convergence. Nowadays, the best numerical method for the solution of most singular problems is the adaptive hp-version of the FEM (hp-FEM). This method is based on spatial refinements toward the singularities combined with optimal variation of polynomial degrees on the elements. The hp-FEM has mathematically proven exponential convergence, and also in practical computations typically it is by several orders of magnitudes faster than standard FEM.
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Tvarové funkce pro hierarchické Hermitovy prvky
Segeth, Karel
In the contribution we derive a hierarchic basis for arbitrary order Hermite finite elements in one spatial dimension. We show that this basis has optimal conditioning properties for the resulting discrete algebraic problem and optimal local (projection based) interpolation propertics. The approach shoum in this contribution shall be the basic tool for design of quality H.SUP.2-conforming elements for beam and plate bending problems.
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