Sökning: "localized suction"

Visar resultat 1 - 5 av 8 avhandlingar innehållade orden localized suction.

1. 1. 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

3. 2. Numerical studies of transtion in wall-bounded flows

   Författare :Ori Levin; Dan Henningson; Nikolaus Adams; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layer; suction; wall jet; streaks; waves; periodic disturbance; localized disturbance; turbulent spot; algebraic growth; exponential growth; stability; transition thresholds; transition prediction; PSE; DNS; Fluid mechanics; Strömningsmekanik;

   Sammanfattning : Disturbances introduced in wall-bounded flows can grow and lead to transition from laminar to turbulent flow. In order to reduce losses or enhance mixing in energy systems, a fundamental understanding of the flow stability and transition mechanism is important. LÄS MER

4. 3. Stability and transition in the suction boundary layer and other shear flows

   Författare :Niklas Davidsson; Luleå tekniska universitet; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Strömningslära; Fluid Mechanics;

   Sammanfattning : Bypass transition has been studied by theoretical and numerical procedures, with the asymptotic suction boundary layer (ASBL) in focus. As reference cases the Blasius boundary layer (BBL) and a free shear flow have been studied. In order to reduce energy losses associated with flow systems, it is a wish to avoid turbulence in these flows. LÄS MER

5. 4. Linear and nonlinear development of perturbations in the asymptotic suction boundary layer

   Författare :Niklas Davidsson; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Strömningslära; Fluid Mechanics;

   Sammanfattning : Turbulent processes play an important role in most flow systems. To optimize and control these flows, knowledge about the mechanisms that leads to and maintains turbulence is crucial. Boundary layers with wall suction are known to delay/prevent transition as well as separation. LÄS MER

7. 5. 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