Sökning: "drag reduction"

Visar resultat 11 - 15 av 57 avhandlingar innehållade orden drag reduction.

  1. 11. Interaction of flows with slender structures and liquid-infused surfaces

    Författare :Johan Sundin; Shervin Bagheri; Daniel Chung; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; flow-structure interactions; flow control; turbulent boundary layers; soft sensors; drag reduction; capillary waves; surfactants; Marangoni stress; mixing enhancement; Engineering Mechanics; Teknisk mekanik;

    Sammanfattning : Surface textures and protrusions can be used to control or gain information about a flow. We investigate the solid-flow interaction of filamentous structures and liquid-infused surfaces (LIS). Both filamentous structures and LIS are used by organisms and can be exploited in technical applications. LÄS MER

  3. 12. Attenuation of boundary layer disturbances by means of streamwise vortices

    Författare :Sohrab Sattarzadeh Shirvan; Jens H. M. Fransson; Valery Chernoray; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layer stability; Tollmien-Schlichting waves; oblique waves; transition to turbulence; streamwise vortices; miniature vortex generators; instability control; drag reduction;

    Sammanfattning : The stability of the boundary layer developed on a flat plate is studied in the presence of streamwise streaks where disturbances of different types are introduced in the wall-bounded shear layer. The experimental investigations are aimed at flow control by means of passively damping the energy growth of the disturbances in the streaky boundary layer and furthermore delay the onset of the transition in the streamwise direction. LÄS MER

  4. 13. 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

  5. 14. Transition delay in boundary-layer flows via reactive control

    Författare :Nicolò Fabbiane; Dan S. Henningson; Shervin Bagheri; Denis Sipp; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; flow control; drag reduction; net energy saving; adaptive control; model-based control; optimal control; flat-plate boundary layer; laminar-to- turbulent transition; plasma actuator; direct numerical simulation; in-flight experiments; strömningsstyrning; friktionsreduktion; netto energibesparing; adaptiv styrning; modellbaserad styrning; optimal kontroll; gränsskikt öve en plan platta; laminärt till turbulent omslag; plasma aktuator; DNS; flyg prov; Engineering Mechanics; Teknisk mekanik;

    Sammanfattning : Transition delay in boundary-layer flows is achieved via reactive control of flow instabilities, i.e. Tollmien-Schlichting (TS) waves. Adaptive and model-based control techniques are investigated by means of direct numerical simulations (DNS) and experiments. LÄS MER

  7. 15. Improvement of the retention-fromation relationship using three-component retention aid systems

    Författare :Anna Svedberg; Lars Wågberg; Janne Laine; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Dewatering; drag reduction; fibre flocculation; filler retention; fine paper; flow imaging; flow loop; formation aid; kraft pulp; magnetic resonance imaging; MRI; paper formation; pilot web former; pressure drop; retention aid; turbulence damping;

    Sammanfattning : .... LÄS MER