Search for dissertations about: "Dynamical Instability"

Showing result 1 - 5 of 31 swedish dissertations containing the words Dynamical Instability.

2. 1. Transition to turbulence in the asymptotic suction boundary layer

   Author : Taras Khapko; Dan Henningson; Philipp Schlatter; Yohann Duguet; Marc Avila; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layers; instability; laminar-turbulent transition; dynamical systems; edge states; near-wall turbulence; laminarisation;

   Abstract : The focus of this thesis is on the numerical study of subcritical transition to turbulence in the asymptotic suction boundary layer (ASBL). Applying constant homogeneous suction prevents the spatial growth of the boundary layer, granting access to the asymptotic dynamics. READ MORE

4. 2. Numerical studies on flows with secondary motion

   Author : Jacopo Canton; Philipp Schlatter; David Moxey; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; nonlinear dynamical systems; instability; bifurcation; flow control; skin-friction reduction; Engineering Mechanics; Teknisk mekanik;

   Abstract : This work is concerned with the study of flow stability and turbulence control - two old but still open problems of fluid mechanics. The topics are distinct and are (currently) approached from different directions and with different strategies. READ MORE

5. 3. Effects of disorder in metallic systems from First-Principles calculations

   Author : Christian Asker; Igor Abrikosov; Jörg Neugebauer; Linköpings universitet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Iron; Nickel; Magnesium; Manganese; Molybdenum; Zirconium; Elastic Constants; High pressure; Earth s core; Density-functional theory; Ab-initio; First-Principles; Core-level shifts; Molecular Dynamics; Phonons; Dynamical Instability; Condensed matter physics; Kondenserade materiens fysik; Computational physics; Beräkningsfysik;

   Abstract : In this thesis, quantum-mechanical calculations within density-functional theory on metallic systems are presented. The overarching goal has been to investigate effects of disorder. In particular, one of the properties investigated is the bindingenergy shifts for core electrons in binary alloys using different theoretical methods. READ MORE

6. 4. Studies on instability and optimal forcing of incompressible flows

   Author : Mattias Brynjell-Rahkola; Dan S. Henningson; Ardeshir Hanifi; Philipp Schlatter; François Gallaire; KTH; []
   Keywords : 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;

   Abstract : 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. READ MORE

7. 5. Cases of coupled vibrations and prametric instability in rotating machines

   Author : Jean-Claude Luneno; Ilmar Santos; Luleå tekniska universitet; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Hållfasthetslära; Solid Mechanics;

   Abstract : The principal task in this research project was to analyse the causes and consequences of coupled vibrations and parametric instability in hydropower rotors; where both horizontal and vertical machines are involved. Vibration is a well-known undesirable behavior of dynamical systems characterised by persistent periodic, quasi-periodic or chaotic motions. READ MORE