Sökning: "Dan S. Henningson"

Visar resultat 1 - 5 av 18 avhandlingar innehållade orden Dan S. Henningson.

  1. 1. Adaptive and model-based control in laminar boundary-layer flows

    Författare :Nicolò Fabbiane; Dan S. Henningson; Aimee S. Morgans; KTH; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Flow control; Control theory; Optimal control; Adaptive control; Boundary-layer flow; Fluid dynamics; Plasma actuator; Surface hot-wire; Transition delay;

    Sammanfattning : In boundary-layer flows it is possible to reduce the friction drag by breaking the path from laminar to turbulent state. In low turbulence environments, the laminar-to-turbulent transition is dominated by local flow instabilities – Tollmien-Schlichting (TS) waves – that exponentially grows while being con- vected by the flow and, eventually, lead to transition. LÄS MER

  2. 2. Modelling and control of turbulent and transitional flows

    Författare :Pierluigi Morra; Dan S. Henningson; Ardeshir Hanifi; André V. G. Cavalieri; Shervin Bagheri; Aimee S. Morgans; KTH; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; reduced order modeling; flow control; resolvent analysis; transi- tional boundary layer; turbulent boundary layer; drag reduction; high-fidelity wall-turbulence modelling; modellreduktion; strömningskontroll; resolvent analys; laminär- turbulent omslag; turbulent gränsskikt; motståndsminskning; väggturbulens modellering; Teknisk mekanik; Engineering Mechanics;

    Sammanfattning : The dynamics of fluid motion can accurately be described by the Navier– Stokes equations. Manipulating these equations to reduce their complexity but preserving their main characteristics has always been a key research activity in the field of fluid mechanics. LÄS MER

  3. 3. Numerical computations of wind turbine wakes

    Författare :Stefan S. A. Ivanell; Dan Henningson; Peinke Joachim; KTH; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Actuator Line Model; Actuator Disc Model; Wind Turbine Wake; CFD; LES; EllipSys3D; Fluid mechanics; Strömningsmekanik;

    Sammanfattning : Numerical simulations of the Navier-Stokes equations are performed to achieve a better understanding of the behaviour of wakes generated by wind turbines. The simulations are performed by combining the in-house developed computer code EllipSys3D with the actuator line and disc methodologies. LÄS MER

  4. 4. Studies on instability and optimal forcing of incompressible flows

    Författare :Mattias Brynjell-Rahkola; Dan S. Henningson; Ardeshir Hanifi; Philipp Schlatter; François Gallaire; KTH; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; 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

  5. 5. Receptivity, Stability and Sensitivity analysis of two- and three-dimensional flows

    Författare :Guillaume Chauvat; Ardeshir Hanifi; Dan S. Henningson; Ulrich Rist; KTH; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary-layers; stability; receptivity; sensitivity; transition; mode decomposition; Teknisk mekanik; Engineering Mechanics;

    Sammanfattning : This work deals with various aspects of boundary-layer stability. Modal and non-modal approaches are first used in the study of the global stability of a jet in crossflow. LÄS MER