Sökning: "Shervin Bagheri"

Visar resultat 1 - 5 av 8 avhandlingar innehållade orden Shervin Bagheri.

  1. 1. Analysis and control of transitional shear flows using global modes

    Författare :Shervin Bagheri; Dan Henningson; Alessandro Bottaro; KTH; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Fluid mechanics; flow control; hydrodynamic stability; global modes; jet in crossflow; flat-plate boundary layer; laminar-turbulent transition; Arnoldi method; Koopman modes; balanced truncation; direct numerical simulations.; Fluid mechanics; Strömningsmekanik;

    Sammanfattning : In this thesis direct numerical simulations are used to investigate two phenomenain shear flows: laminar-turbulent transition over a flat plate and periodicvortex shedding induced by a jet in cross flow. The emphasis is on understanding and controlling the flow dynamics using tools from dynamical systems and control theory. LÄS MER

  2. 2. Stability analysis and control design of spatially developing flows

    Författare :Shervin Bagheri; Dan Henningson; Martin Berggren; KTH; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Global modes; transient growth; model reduction; feedback control; Fluid mechanics; Strömningsmekanik;

    Sammanfattning : Methods in hydrodynamic stability, systems and control theory are applied to spatially developing flows, where the flow is not required to vary slowly in the streamwise direction. A substantial part of the thesis presents a theoretical framework for the stability analysis, input-output behavior, model reduction and control design for fluid dynamical systems using examples on the linear complex Ginzburg-Landau equation. LÄS MER

  3. 3. Active Control and Reduced-Order Modeling of Transition in Shear Flows

    Författare :Reza Dadfar; Dan S. Henningson; Ardeshir Hanifi; Shervin Bagheri; Vassilis Theofilis; KTH; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; SRA - E-Science SeRC ; SRA - E-vetenskap SeRC ;

    Sammanfattning : In this thesis direct numerical simulation is used to investigate the possibilityto delay the transition from laminar to turbulent in boundary layer flows.Furthermore, modal analysis is used to reveal the coherent structures in highdimensional dynamical systems arising in the flow problems. LÄS MER

  4. 4. Transition delay in boundary-layer flows via reactive control

    Författare :Nicolò Fabbiane; Dan S. Henningson; Shervin Bagheri; Denis Sipp; KTH; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; 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; Teknisk mekanik; Engineering Mechanics;

    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

  5. 5. Models of porous, elastic and rigid materials in moving fluids

    Författare :Ugis Lacis; Shervin Bagheri; Fredrik Lundell; Lakshminarayanan Mahadevan; KTH; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; fluid-structure-interaction; flow control; passive appendages; homogenization; poroelastic coatings; separated flows; surface-fluid interface; fluid-struktur-interaktion; flödeskontroll; passiva utväxter; homogenisering; ytbeläggning; separerade strömning; ytbeläggning-strömning gränssnitt; Teknisk mekanik; Engineering Mechanics;

    Sammanfattning : Tails, fins, scales, and surface coatings are used by organisms for various tasks, including locomotion. Since millions of years of evolution have passed, we expect that the design of surface structures is optimal for the tasks of the organism. These structures serve as an inspiration in this thesis to identify new mechanisms for flow control. LÄS MER