Sökning: "boundary-layer suction"

Visar resultat 1 - 5 av 32 avhandlingar innehållade orden boundary-layer suction.

1. 1. Experimental study on turbulent boundary-layer flows with wall transpiration

   Författare :Marco Ferro; Jens Fransson; Bengt Fallenius; Joseph Klewicki; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Turbulent boundary layer; boundary-layer suction; boundary-layer blowing; wall-bounded turbulent flows; self-sustained turbulence; Engineering Mechanics; Teknisk mekanik;

   Sammanfattning : Wall transpiration, in the form of wall-normal suction or blowing through a permeable wall, is a relatively simple and effective technique to control the behaviour of a boundary layer. For its potential applications for laminar-turbulent transition and separation delay (suction) or for turbulent drag reduction and thermal protection (blowing), wall transpiration has over the past decades been the topic of a significant amount of studies. LÄS MER

3. 2. Optimisation and control of boundary layer flows

   Författare :Antonios Monokrousos; Dan S. Henningson; Per Lötstedt; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layer; control; estimation; optimal disturbances; Lagrange method; Engineering mechanics; Teknisk mekanik;

   Sammanfattning : Both optimal disturbances and optimal control are studied by means of numerical simulations for the case of the flat-plate boundary-layer flow. The optimisation method is the Lagrange multiplier technique where the objective function is the kinetic energy of the flow perturbations and the constraints involve the linearised Navier–Stokes equations. LÄS MER

4. 3. Investigations of the asymptotic suction boundary layer

   Författare :Jens H. M. Fransson; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Asymptotic suction boundary layer; Laminar-turbulent transition; Tollmien-Schlichting waves; Free stream turbulence; Engineering mechanics; Teknisk mekanik;

   Sammanfattning : .... LÄS MER

5. 4. Boundary layer streaks as a novel laminar flow control method

   Författare :Sohrab Sattarzadeh Shirvan; Jens H. M. Fransson; Edward B. White; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layer stability; laminar to turbulent transition; laminar flow control; drag reduction; Tollmien-Schlichting waves; oblique waves; streaky boundary layers; miniature vortex generators; discrete suction;

   Sammanfattning : A novel laminar flow control based on generation of spanwise mean velocity gradients (SVG) in a flat plate boundary layer is investigated where disturbances of different types are introduced in the wall-bounded shear layer. The experimental investigations are aimed at; (i) generating stable and steady streamwise streaks in the boundary layer which set up spanwise gradients in the mean flow, and (ii) attenuating disturbance energy growth in the streaky boundary layers and hence delaying the onset of turbulence transition. LÄS MER

7. 5. Vortex generators and turbulent boundary layer separation control

   Författare :Ola Lögdberg; Henrik Alfredsson; Per-Åge Krogstad; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; turbulent boundary layer separation; adverse pressure gradient; vortex generators; control of separation; Fluid mechanics; Strömningsmekanik;

   Sammanfattning : Boundary layer separation is usually an unwanted phenomenon in most technical applications as for instance on airplane wings, on ground vehicles and in internal flows such as diffusers. If separation occurs it leads to loss of lift, higher drag and results in energy losses. LÄS MER