Sökning: "nonlinear perturbation"

Visar resultat 16 - 20 av 35 avhandlingar innehållade orden nonlinear perturbation.

  1. 16. Degenerating Orr-Sommerfeld eigenmodes and development of three-dimensional perturbations

    Författare :Rajaratnam Shanthini; Luleå tekniska universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Strömningslära; Fluid Mechanics;

    Sammanfattning : Degeneracies of temporally damped Orr-Sommerfeld eigenmodes are studied primarily for plane Poiseuille flow. The discrete spectrum of the eigenmodes is shown to possess infinitely many degeneracies, each appearing at a certain combination of k (the modulus of resultant wavenumber) and α R (the streamwise wavenumber times the Reynolds number). LÄS MER

  3. 17. Feedback and adjoint based control of boundary layer flows

    Författare :Mattias Chevalier; Dan Henningson; Jean-Marc Chomaz; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Applied mechanics; fluid and plasma; mechanical engineering; Teknisk mekanik; Engineering mechanics; Teknisk mekanik;

    Sammanfattning : Linear and nonlinear optimal control have been investigated in transitional channel and boundary layer .ows. The flow phenomena that we study are governed by the incompressible Navier–Stokes equations and the main aim with the control is to prevent transition from laminar to turbulent flows. LÄS MER

  4. 18. Stability and transition of three-dimensional boundary layers

    Författare :Seyed Mohammad Hosseini; Ardeshir Hanifi; Vassilios Theofilis; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Receptivity; stability; optimal growth; three-dimensional boundary layers; crossflow instability; roughness control; freestream turbulence; secondary instability;

    Sammanfattning : A focus has been put on the stability characteristics of different flow types existing on air vehicles. Flow passing over wings and different junctions on an aircraft face numerous local features, ranging from different pressure gradients, to interacting boundary layers. LÄS MER

  5. 19. Least squares methods and applications in robotics

    Författare :Bertil Waldén; Wedin Per-Åke; Linköpings universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

    Sammanfattning : This thesis consider the least squares problems and various applications to the inverse kinematic problem in robotics. Two main linear least squares results are given; new backward perturbation bounds and an adaptive algorithm for rank-I regularization for rank deficient linear least squares problems. The inverse kinematic problem, i.e. LÄS MER

  7. 20. Numerical studies of bypass transition in the Blasius boundary layer

    Författare :Luca Brandt; KTH; []
    Nyckelord :Fluid Mechanics; laminar-turbulent transition; boundary layer flow; transient growth; streamwise streaks; secondary instability;

    Sammanfattning : Experimental findings show that transition from laminar toturbulent ow may occur also if the exponentially growingperturbations, eigensolutions to the linearised disturbanceequations, are damped. An alternative non-modal growthmechanism has been recently identi fied, also based on thelinear approximation. LÄS MER