Sökning: "Blasius"

Visar resultat 1 - 5 av 12 avhandlingar innehållade ordet Blasius.

1. 1. Global stability analysis of three-dimensional boundary layer flows

   Författare :Mattias Brynjell-Rahkola; Dan Henningson; Philipp Schlatter; Ardeshir Hanifi; Spencer Sherwin; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Hydrodynamic stability; transition to turbulence; global analysis; boundary layers; roughness; laminar flow control; Stokes Laplace preconditioner; optimal forcing; crossflow vortices; Ginzburg-Landau; Falkner-Skan-Cooke; Blasius; lid-driven cavity;

   Sammanfattning : This thesis considers the stability and transition of incompressible boundary layers. In particular, the Falkner–Skan–Cooke boundary layer subject to a cylindrical surface roughness, and the Blasius boundary layer with applied localized suction are investigated. LÄS MER

3. 2. 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

4. 3. 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

5. 4. Studies on instability and optimal forcing of incompressible flows

   Författare :Mattias Brynjell-Rahkola; Dan S. Henningson; Ardeshir Hanifi; Philipp Schlatter; François Gallaire; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; hydrodynamic stability; optimal forcing; resolvent operator; Laplace preconditioner; spectral element method; eigenvalue problems; inverse power method; direct numerical simulations; Falkner–Skan–Cooke boundary layer; localized roughness; crossflow vortices; Blasius boundary layer; localized suction; helical vortices; lid-driven cavity; cylinder flow; Teknisk mekanik; Engineering Mechanics;

   Sammanfattning : This thesis considers the hydrodynamic instability and optimal forcing of a number of incompressible flow cases. In the first part, the instabilities of three problems that are of great interest in energy and aerospace applications are studied, namely a Blasius boundary layer subject to localized wall-suction, a Falkner–Skan–Cooke boundary layer with a localized surface roughness, and a pair of helical vortices. LÄS MER

7. 5. Nonlinear dynamics in transitional wall-bounded flows

   Författare :Miguel Beneitez Galan; Dan S. Henningson; Philipp Schlatter; Yohann Duguet; Tobias Schneider; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Engineering Mechanics; Teknisk mekanik;

   Sammanfattning : This thesis focuses on numerical studies of subcritical transition to turbulence in shear flows. The thesis employs a framework based on nonlinear dynamics in the subsequent studies. The geometrical approach to subcritical transition pivots the concepts of edge manifold and edge state. LÄS MER