Sökning: "streamwise streaks"

Visar resultat 1 - 5 av 31 avhandlingar innehållade orden streamwise streaks.

  1. 1. Study of generation, growth and breakdown of streamwise streaks in a Blasius boundary layer

    Författare :Luca Brandt; KTH; []
    Nyckelord :Fluid mechanics; laminar-turbulent transition; boundary layer flow; transient growth; streamwise streaks; lift-up effect; receptivity; free-stream turbulence; streak instability; secondary instability; Direct Numerical Simulation.;

    Sammanfattning : Transition from laminar to turbulent flow has beentraditionally studied in terms of exponentially growingeigensolutions to the linearized disturbance equations.However, experimental findings show that transition may occuralso for parameters combinations such that these eigensolutionsare damped. LÄS MER

  3. 2. Attenuation of boundary layer disturbances by means of streamwise vortices

    Författare :Sohrab Sattarzadeh Shirvan; Jens H. M. Fransson; Valery Chernoray; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layer stability; Tollmien-Schlichting waves; oblique waves; transition to turbulence; streamwise vortices; miniature vortex generators; instability control; drag reduction;

    Sammanfattning : The stability of the boundary layer developed on a flat plate is studied in the presence of streamwise streaks where disturbances of different types are introduced in the wall-bounded shear layer. The experimental investigations are aimed at flow control by means of passively damping the energy growth of the disturbances in the streaky boundary layer and furthermore delay the onset of the transition in the streamwise direction. LÄS MER

  4. 3. Numerical studies of bypass transition in the Blasius boundary layer

    Författare :Luca Brandt; KTH; []
    Nyckelord :Fluid Mechanics; laminar-turbulent transition; boundary layer flow; transient growth; streamwise streaks; secondary instability;

    Sammanfattning : Experimental findings show that transition from laminar toturbulent ow may occur also if the exponentially growingperturbations, eigensolutions to the linearised disturbanceequations, are damped. An alternative non-modal growthmechanism has been recently identi fied, also based on thelinear approximation. LÄS MER

  5. 4. Stability analysis and transition prediction of wall-bounded flows

    Författare :Ori Levin; KTH; []
    Nyckelord :Boundary layer; wall jet; algebraic growth; exponential growth; lift-up effect; streamwise streaks; Tollmien-Schlichting waves; free-stream turbulence; roughness element; transition prediction; Parabolized Stability Equations; Direct Numerical S;

    Sammanfattning : Disturbances introduced in wall-bounded .ows can grow andlead to transition from laminar to turbulent .ow. In order toreduce losses or enhance mixing in energy systems, afundamental understanding of the . LÄS MER

  7. 5. Hydrodynamics of plane liquid jets aimed at applications in paper manufacturing

    Författare :Daniel Söderberg; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; liquid jet; transition; break-up; stability; wavelet; free surface; waves; streamwise streaks; fibre suspension; headbox; forming; shadowgraph; hot-film; Engineering mechanics; Teknisk mekanik;

    Sammanfattning : Process industries are in general depending, in one way or the other, on fluid mechanics.Specifically, paper manufacturing, which probably is the dominant processindustry in Sweden, is depending on the flow of cellulose fibres suspended in water. LÄS MER