Sökning: "transition to turbulence"

Visar resultat 1 - 5 av 104 avhandlingar innehållade orden transition to turbulence.

  1. 1. Edge states and transition to turbulence in boundary layers

    Författare :Taras Khapko; Dan Henningson; Philipp Schlatter; Yohann Duguet; Rich Kerswell; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layer; transition to turbulence; direct numerical simulation; edge state; free-stream turbulence; bypass transition; probabilistic cellular automaton; turbulence at the onset; laminar–turbulent coexistence; laminarisation; Engineering Mechanics; Teknisk mekanik;

    Sammanfattning : The focus of this thesis is the numerical study of subcritical transition to turbulence in boundary-layer flows. For the most part, boundary layers with uniform suction are considered. Constant homogeneous suction counteracts the spatial growth of the boundary layer, rendering the flow parallel. LÄS MER

  3. 2. On stability, transition and turbulence in three-dimensional boundary-layer flows

    Författare :Seyed Mohammd Hosseini; Ardeshir Hanifi; Spencer Sherwin; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Receptivity; stability; optimal growth; three-dimensional bound- ary layers; crossflow instability; roughness control; freestream turbulence; sec- ondary instability; transition; turbulence;

    Sammanfattning : A lot has changed since that day on December 17, 1903 when the Wright brothers made the first powered manned flight. Even though the concepts behind flying are unaltered, appearance of stat-of-the-art modern aircrafts has undergone a massive evolution. LÄS MER

  4. 3. Spectral-element simulations of turbulent wall-bounded flows including transition and separation

    Författare :Johan Malm; Dan Henningson; Philipp Schlatter; Suad Jakirlic; KTH; []
    Nyckelord :spectral-element method; direct numerical simulation DNS ; large-eddy simulation LES ; turbulence; transition; over-integration; three-dimensional separation; massively parallel simulations; proper orthogonal decomposition POD ; Koopman modes; vorticity stretching; coherence; SRA - E-vetenskap SeRC ; SRA - E-Science SeRC ;

    Sammanfattning : The spectral-element method (SEM) is used to study wall-bounded turbulent flowsin moderately complex geometries. The first part of the thesis is devoted to simulations of canonical flow cases, such as temporal K-type transitionand turbulent channel flow, to investigate general resolution requirements and computational efficiency of the numerical code nek5000. LÄS MER

  5. 4. Transition to turbulence in the asymptotic suction boundary layer

    Författare :Taras Khapko; Dan Henningson; Philipp Schlatter; Yohann Duguet; Marc Avila; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layers; instability; laminar-turbulent transition; dynamical systems; edge states; near-wall turbulence; laminarisation;

    Sammanfattning : The focus of this thesis is on the numerical study of subcritical transition to turbulence in the asymptotic suction boundary layer (ASBL). Applying constant homogeneous suction prevents the spatial growth of the boundary layer, granting access to the asymptotic dynamics. LÄS MER

  7. 5. Transition in Particle-laden Flows

    Författare :Joy Klinkenberg; Luca Brandt; Shuisheng He; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Transition; modal analysis; non-modal analysis; multi-phase flow; particle-laden; heavy particles; light particles;

    Sammanfattning : This thesis presents the study of laminar to turbulent transition of particle laden flows. When a flow becomes turbulent, the drag increases one order of magnitude compared to a laminar flow, therefore, much research is devoted to understand and influence the transition. LÄS MER