Sökning: "laminar-to- turbulent transition"

Visar resultat 6 - 10 av 21 avhandlingar innehållade orden laminar-to- turbulent transition.

  1. 6. Active Control and Modal Structures in Transitional Shear Flows

    Författare :Onofrio Semeraro; Dan Henningson; Bernd Noack; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Flow control; flat-plate boundary layer; optimal controllers; model reduction; turbulent jet; POD; DMD; Koopman modes;

    Sammanfattning : Flow control of transitional shear flows is investigated by means of numerical simulations. The attenuation of three-dimensional wavepackets of Tollmien-Schlichting (TS) and streaks in the boundary layer is obtained using active control in combination with localised sensors and actuators distributed near the rigid wall. LÄS MER

  3. 7. Active Control and Reduced-Order Modeling of Transition in Shear Flows

    Författare :Reza Dadfar; Dan S. Henningson; Ardeshir Hanifi; Shervin Bagheri; Vassilis Theofilis; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; SRA - E-Science SeRC ; SRA - E-vetenskap SeRC ;

    Sammanfattning : In this thesis direct numerical simulation is used to investigate the possibilityto delay the transition from laminar to turbulent in boundary layer flows.Furthermore, modal analysis is used to reveal the coherent structures in highdimensional dynamical systems arising in the flow problems. LÄS MER

  4. 8. Flow control and reduced-order modelling of transition in shear flows

    Författare :Reza Dadfar; Dan Henningson; Vasssilis Theofilis; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Flow control; plasma actuator; wing; leading edge; flat plate; wind turbine; optimal controller; model reduction; proper orthogonal decomposition; dynamic mode decomposition.;

    Sammanfattning : In this thesis direct numerical simulation is used to investigate the possibility to delay the transition from a laminar to a turbulent flow in boundary layer flows. Furthermore, modal analysis techniques are used to identify the coherent structures in wind turbine wake. LÄS MER

  5. 9. 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. 10. Turbulence Transport Modelling in Gas Turbine Related Applications

    Författare :Andreas Sveningsson; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; RANS; secondary flow; realizability; V2F; transition;

    Sammanfattning : Computational fluid dynamics is a cornerstone in gas turbine engine design. It is used to optimize shapes of turbine and compressor airfoils, to predict heat transfer to gas turbine hot parts, to reduce the amount of pollutants that form when fuel is burnt, to reduce gas turbine noise and so on. LÄS MER