Sökning: "Prescribed boundary layer"

Visar resultat 1 - 5 av 9 avhandlingar innehållade orden Prescribed boundary layer.

  1. 1. Numerical Computations of Wakes Behind Wind Farms : A tool to study Farm to Farm interaction

    Författare :Ola Eriksson; Stefan Ivanell; Anna Rutgersson; Simon-Philippe Breton; Philippe Chatelain; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Wind turbine; Wind power; Wind farm; Wakes; Long distance wakes; Farm-Farm; Farm to farm interaction; Wind farm cluster; Large Eddy simulations; LES; Actuator disc method; ACD; CFD; Ellipsys3D; Prescribed boundary layer; PBL; Forced boundary layer; FBL; Meteorologi; Meteorology;

    Sammanfattning : More and larger wind farms are planned offshore. As the most suitable sites to build are limited these new wind farms will be constructed near to each other in so called wind farm clusters. Behind the wind turbines in these farms there is a disrupted flow of air called a wake that is characterized by reduced wind speed and increased turbulence. LÄS MER

  3. 2. 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

  4. 3. Direct Numerical Simulation of Boundary-layer Transition with Free-stream Turbulence

    Författare :Kristina Durovic; Dan Henningson; Ardeshir Hanifi; Philipp Schlatter; Tamer Zaki; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Engineering Mechanics; Teknisk mekanik;

    Sammanfattning : This thesis considers the generation and influence of free-stream turbulence toboundary layer transition on both flat and curved bodies in the flow. Variousflow configurations such as flow around the flat plate with a sharp leading edgeand low-pressure turbine blades are considered. LÄS MER

  5. 4. Stability and transition in the suction boundary layer and other shear flows

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

    Sammanfattning : Bypass transition has been studied by theoretical and numerical procedures, with the asymptotic suction boundary layer (ASBL) in focus. As reference cases the Blasius boundary layer (BBL) and a free shear flow have been studied. In order to reduce energy losses associated with flow systems, it is a wish to avoid turbulence in these flows. LÄS MER

  7. 5. Contribution to Numerical and Experimental Studies of Flutter in Space Turbines. Aerodynamic Analysis of Subsonic or Supersonic Flows in Response to a Prescribed Vibratory Mode of the Structure

    Författare :Hakim Ferria; Pascal Ferrand; Torsten Fransson; François Moyroud; France Ecole Centrale de Lyon Laboratoire de Mécanique des Fluides et d'Acoustique; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; flutter; space turbine; LRANS computation; flutter measurement; shock wave boundary layer interaction; blisk; cut-on cut-off condition; interblade phase angle; combined modes;

    Sammanfattning : Modern turbomachines are designed towards thinner, lighter and highly loaded blades. This gives rise to increased sensitivity to flow induced vibrations such as flutter, which leads to structure failure in a short period of time if not sufficiently damped. LÄS MER