Sökning: "localized disturbance"

Visar resultat 1 - 5 av 13 avhandlingar innehållade orden localized disturbance.

  1. 1. Numerical studies of transtion in wall-bounded flows

    Författare :Ori Levin; Dan Henningson; Nikolaus Adams; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layer; suction; wall jet; streaks; waves; periodic disturbance; localized disturbance; turbulent spot; algebraic growth; exponential growth; stability; transition thresholds; transition prediction; PSE; DNS; Fluid mechanics; Strömningsmekanik;

    Sammanfattning : Disturbances introduced in wall-bounded flows can grow and lead to transition from laminar to turbulent flow. In order to reduce losses or enhance mixing in energy systems, a fundamental understanding of the flow stability and transition mechanism is important. LÄS MER

  3. 2. Stability and transition in the suction boundary layer and other shear flows

    Författare :Niklas Davidsson; Luleå tekniska universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Strömningslära; Fluid Mechanics;

    Sammanfattning : Bypass transition has been studied by theoretical and numerical procedures, with the asymptotic suction boundary layer (ASBL) in focus. As reference cases the Blasius boundary layer (BBL) and a free shear flow have been studied. In order to reduce energy losses associated with flow systems, it is a wish to avoid turbulence in these flows. LÄS MER

  4. 3. Stability of plane Couette flow and pipe Poiseuille flow

    Författare :Per-Olov Åsén; Gunilla Kreiss; Jonathan Goodman; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Hydrodynamic stability; plane Couette flow; pipe Poiseuille flow; direct numerical simulations; resolvent; Fluid mechanics; Strömningsmekanik;

    Sammanfattning : This thesis concerns the stability of plane Couette flow and pipe Poiseuille flow in three space dimensions. The mathematical model for both flows is the incompressible Navier--Stokes equations. Both analytical and numerical techniques are used. We present new results for the resolvent corresponding to both flows. LÄS MER

  5. 4. Linear and nonlinear development of perturbations in the asymptotic suction boundary layer

    Författare :Niklas Davidsson; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Strömningslära; Fluid Mechanics;

    Sammanfattning : Turbulent processes play an important role in most flow systems. To optimize and control these flows, knowledge about the mechanisms that leads to and maintains turbulence is crucial. Boundary layers with wall suction are known to delay/prevent transition as well as separation. LÄS MER

  7. 5. Traces of Repolarization Inhomogeneity in the ECG

    Författare :Milos Kesek; Anders Englund; Bertil Lindahl; Markku Mäkijärvi; Uppsala universitet; []
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Internal medicine; cardiology; repolarization; ECG; QT dispersion; nondipolar components; T-wave; principal component analysis; repolarization inhomogeneity; Invärtesmedicin; Internal medicine; Invärtesmedicin;

    Sammanfattning : Repolarization inhomogeneity is arrhythmogenic. QT dispersion (QTd) is an easily accessible ECG-variable, related to the repolarization and shown to carry prognostic information. It was originally thought to reflect repolarization inhomogeneity. Lately, arguments have been risen against this hypothesis. LÄS MER