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Visar resultat 1 - 5 av 9 avhandlingar som matchar ovanstående sökkriterier.

1. 1. Studies on instability and optimal forcing of incompressible flows

   Författare :Mattias Brynjell-Rahkola; Dan S. Henningson; Ardeshir Hanifi; Philipp Schlatter; François Gallaire; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; hydrodynamic stability; optimal forcing; resolvent operator; Laplace preconditioner; spectral element method; eigenvalue problems; inverse power method; direct numerical simulations; Falkner–Skan–Cooke boundary layer; localized roughness; crossflow vortices; Blasius boundary layer; localized suction; helical vortices; lid-driven cavity; cylinder flow; Teknisk mekanik; Engineering Mechanics;

   Sammanfattning : This thesis considers the hydrodynamic instability and optimal forcing of a number of incompressible flow cases. In the first part, the instabilities of three problems that are of great interest in energy and aerospace applications are studied, namely a Blasius boundary layer subject to localized wall-suction, a Falkner–Skan–Cooke boundary layer with a localized surface roughness, and a pair of helical vortices. LÄS MER

3. 2. Parallelization of dynamic algorithms for electronic structure calculations

   Författare :Anton G. Artemov; Emanuel H. Rubensson; Maya Neytcheva; Bo Kågström; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; parallelization; task-based programming; matrix algorithms; sparse matrices; inverse factorization; localized computations; density matrix methods; electronic structure calculations; Scientific Computing; Beräkningsvetenskap;

   Sammanfattning : The aim of electronic structure calculations is to simulate behavior of complex materials by resolving interactions between electrons and nuclei in atoms at the level of quantum mechanics. Progress in the field allows to reduce the computational complexity of the solution methods to linear so that the computational time scales proportionally to the size of the physical system. LÄS MER

4. 3. On discontinuous Galerkin multiscale methods

   Författare :Daniel Elfverson; Axel Målqvist; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Beräkningsvetenskap med inriktning mot numerisk analys; Scientific Computing with specialization in Numerical Analysis;

   Sammanfattning : In this thesis a new multiscale method, the discontinuous Galerkin multiscale method, is proposed. The method uses localized fine scale computations to correct a global coarse scale equation and thereby takes the fine scale features into account. LÄS MER

5. 4. Electronic Structure and Core-Hole Dynamics of Ozone : Synchrotron-radiation based studies and ab-initio calculations

   Författare :Karoline Wiesner; Svante Svensson; Olle Björneholm; Robert E. Continetti; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Physics; Fysik; Physics; Fysik;

   Sammanfattning : The electronic structure of the ozone molecule O3 has been studied with spectroscopy techniques and computations. The investigation was focused on O3 in a core-hole state. The electronic configuration and the nuclear dynamics have been found to be highly correlated. LÄS MER

7. 5. Multiscale Methods and Uncertainty Quantification

   Författare :Daniel Elfverson; Axel Målqvist; Frédéric Legoll; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; multiscale methods; finite element method; discontinuous Galerkin; Petrov-Galerkin; a priori; a posteriori; complex geometry; uncertainty quantification; multilevel Monte Carlo; failure probability; Beräkningsvetenskap med inriktning mot numerisk analys; Scientific Computing with specialization in Numerical Analysis;

   Sammanfattning : In this thesis we consider two great challenges in computer simulations of partial differential equations: multiscale data, varying over multiple scales in space and time, and data uncertainty, due to lack of or inexact measurements.We develop a multiscale method based on a coarse scale correction, using localized fine scale computations. LÄS MER