Sökning: "global stability"

Visar resultat 1 - 5 av 260 avhandlingar innehållade orden global stability.

  1. 1. Global stability and feedback control of boundary layer flows

    Författare :Espen Åkervik; Dan S. Henningson; Luca Brandt; Dwight Barkley; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Stability; Global Stability; Feedback Control; Control; Estimation; Absolute Convective Instabilities; Model Reduction; Fluid mechanics; Strömningsmekanik;

    Sammanfattning : In this thesis the stability of generic boundary layer flows is studied from a global viewpoint using optimization methods. Global eigenmodes of the incompressible linearized Navier-Stokes equations are computed using the Krylov subspace Arnoldi method. LÄS MER

  3. 2. Global stability analysis of three-dimensional boundary layer flows

    Författare :Mattias Brynjell-Rahkola; Dan Henningson; Philipp Schlatter; Ardeshir Hanifi; Spencer Sherwin; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Hydrodynamic stability; transition to turbulence; global analysis; boundary layers; roughness; laminar flow control; Stokes Laplace preconditioner; optimal forcing; crossflow vortices; Ginzburg-Landau; Falkner-Skan-Cooke; Blasius; lid-driven cavity;

    Sammanfattning : This thesis considers the stability and transition of incompressible boundary layers. In particular, the Falkner–Skan–Cooke boundary layer subject to a cylindrical surface roughness, and the Blasius boundary layer with applied localized suction are investigated. LÄS MER

  4. 3. Computer-Assisted Proofs and Other Methods for Problems Regarding Nonlinear Differential Equations

    Författare :Oswald Fogelklou; Warwick Tucker; Gunilla Kreiss; Piotr Zgliczynski; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; computer-assisted proof; numerical verification; viscous Burgers’ equation; enclosure; existence; nonlinear boundary value problems; Euler equations; inverse problem; bicubic spline; interval analysis; heat equation; fluid limit; peer-to-peer networks; fixed points; stability; global stability; Mathematics; Matematik;

    Sammanfattning : This PhD thesis treats some problems concerning nonlinear differential equations. In the first two papers computer-assisted proofs are used. The differential equations there are rewritten as fixed point problems, and the existence of solutions are proved. LÄS MER

  5. 4. Stability and complexity of ecosystems - Global interaction constraints, landscape and extinctions

    Författare :Susanne Pettersson; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Complexity; Collapse; Stability; Ecosystems; Extinctions; Population dynamics; spatial heterogeneity; Dynamical systems; dispersal;

    Sammanfattning : Human society's expansion and demand for both biotic and abiotic natural resources exert a large pressure on ecosystems around the globe. Ecosystems are complex networks of species interacting with each other and their physical surroundings. LÄS MER

  7. 5. Global stability analysis of complex fluids

    Författare :Iman Lashgari; Luca Brandt; Francois Gallaire; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; non-Newtonian flow; Carreau model; Oldroyd-B model; FENE-P model; modal analysis; nonmodal analysis; sensitivity analysis;

    Sammanfattning : The main focus of this work is on the non-Newtonian effects on the inertial instabilities in shear flows. Both inelastic (Carreau) and elastic models (Oldroyd-B and FENE-P) have been employed to examine the main features of the non-Newtonian fluids; shear-thinning, shear-thickening and elasticity. LÄS MER