Sökning: "streamwise streaks"

Visar resultat 11 - 15 av 31 avhandlingar innehållade orden streamwise streaks.

  1. 11. Experiments on oblique transition in wall bounded shear flows

    Författare :Per Elofsson; KTH; []
    Nyckelord :;

    Sammanfattning : This thesis considers laminar-turbulent transition in wall bounded shear flows, with a focus on transition emanating from a pair of oblique disturbance waves. The oblique waves interact nonlinearly and transfers disturbance energy into streamwise vortices, which generate streamwise streaks through a linear mechanism that operates also at conditions where stability theory predicts decay of all eigenmodes. LÄS MER

  3. 12. Stability analysis and control design of spatially developing flows

    Författare :Shervin Bagheri; Dan Henningson; Martin Berggren; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Global modes; transient growth; model reduction; feedback control; Fluid mechanics; Strömningsmekanik;

    Sammanfattning : Methods in hydrodynamic stability, systems and control theory are applied to spatially developing flows, where the flow is not required to vary slowly in the streamwise direction. A substantial part of the thesis presents a theoretical framework for the stability analysis, input-output behavior, model reduction and control design for fluid dynamical systems using examples on the linear complex Ginzburg-Landau equation. LÄS MER

  4. 13. Experimental studies of bypass transition and its control

    Författare :Fredrik Lundell; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; fluid mechanics; active control; Laminar-turbulent transition; free-stream turbulence; Engineering mechanics; Teknisk mekanik;

    Sammanfattning : Bypass transition, i.e. transition of a boundary layer at subcritical Reynolds numbers, has been studied. Fundamental studies of the phenomenon as such have been performed side by side with experiments aimed at controlling, i. LÄS MER

  5. 14. Oblique waves in boundary layer transition

    Författare :Stellan Berlin; KTH; []
    Nyckelord :;

    Sammanfattning : Traditional research on laminar-turbulent transition has focused on scenarios that are caused by the exponential growth of eigensolutions to the linearized disturbance equations, e.g. two-dimensional Tollmien-Schlichting waves. LÄS MER

  7. 15. Optimisation and control of boundary layer flows

    Författare :Antonios Monokrousos; Dan S. Henningson; Per Lötstedt; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layer; control; estimation; optimal disturbances; Lagrange method; Engineering mechanics; Teknisk mekanik;

    Sammanfattning : Both optimal disturbances and optimal control are studied by means of numerical simulations for the case of the flat-plate boundary-layer flow. The optimisation method is the Lagrange multiplier technique where the objective function is the kinetic energy of the flow perturbations and the constraints involve the linearised Navier–Stokes equations. LÄS MER