Sökning: "global stabilitet"

Visar resultat 1 - 5 av 24 avhandlingar innehållade orden global stabilitet.

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. Space-adaptive simulation of transition and turbulence in shear flows

   Författare :Daniele Massaro; Philipp Schlatter; Saleh Rezaeiravesh; Alfredo Pinelli; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Turbulence; global stability; coherent structures; adaptive mesh refinement; Turbulens; global stabilitet; koherenta strukturer; adaptiv nätförfining; Teknisk mekanik; Engineering Mechanics;

   Sammanfattning : Transitional and turbulent shear flows are ubiquitous, from the boundary layer developing on an aeroplane wing to the flow within the aortic arch. In this thesis, we study wall-bounded and free shear flows through direct numerical simulations. LÄS MER

4. 3. Shapes of pipes

   Författare :Valerio Lupi; Philipp Schlatter; Ramis Örlü; Jean-Christophe Robinet; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Global stability; curved pipes; secondary flow; wall-bounded turbulence; Global stabilitet; krökta rör; sekundärflöde; turbulens; Teknisk mekanik; Engineering Mechanics;

   Sammanfattning : Curved pipes are ubiquitous in several industrial applications and biological systems. The study of flows through these configurations is therefore of significant practical interest.In the present thesis, the modal stability of flows in both toroidal and spatially developing bent pipes is investigated to understand the onset of transition. LÄS MER

5. 4. On stability and receptivity of boundary-layer flows

   Författare :Nima Shahriari; Ardeshir Hanifi; Dan S. Henningson; Peter J. Schmid; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layer receptivity; acoustic receptivity; swept-wing flow; crossflow vortices; roughness element; global stability analysis; direct numerical simulation; plasma actuator; Engineering Mechanics; Teknisk mekanik;

   Sammanfattning : This work is concerned with stability and receptivity analysis as well as studies on control of the laminar-turbulent transition in boundary-layer flows through direct numerical simulations. Various flow configurations are considered to address flow around straight and swept wings. LÄS MER

7. 5. Simulation of individual cells in flow

   Författare :Lailai Zhu; Luca Brandt; Michael Graham; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Hydrodynamic interaction; swimming microorganisms; capsule; Stokes flow; finite element method; boundary integral method; general geometry Ewald method; spectral element method; viscoelastic fluid; cellular deformation; flow cytometry; cell sorting; microrheology; Teknisk mekanik; Engineering Mechanics;

   Sammanfattning : In this thesis, simulations are performed to study the motion ofindividual cells in flow, focusing on the hydrodynamics of actively swimming cells likethe self-propelling microorganisms, and of passively advected objects like the red bloodcells. In particular, we develop numerical tools to address the locomotion ofmicroswimmers in viscoelastic fluids and complex geometries, as well as the motion ofdeformable capsules in micro-fluidic flows. LÄS MER