Sökning: "turbulence models"

Visar resultat 1 - 5 av 286 avhandlingar innehållade orden turbulence models.

  1. 1. Optical Turbulence Characterization for Ground-Based Astronomy

    Författare :Susanna Hagelin; Anna Rutgersson; Elena Masciadri; Valentina Zitelli; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; site testing; atmospheric effects; turbulence; optical turbulence; applied meteorology; mesoscale models; Meteorology; Meteorologi; Astronomy and astrophysics; Astronomi och astrofysik; Meteorologi; Meteorology;

    Sammanfattning : The optical turbulence, which creates perturbations of the wavefronts coming from the stars, is caused by small-scale fluctuations in the index of refraction of the atmosphere and is a problem for astronomers because it limits the maximum resolution of the ground-based telescopes. One way of identifying the best sites to build astronomical observatories, where the influence of the optical turbulence is as small as possible, is to use the standard meteorological parameters to get a first idea of the potential of a site. LÄS MER

  3. 2. Modeling of magnetohydrodynamic turbulence

    Författare :Ola Widlund; KTH; []
    Nyckelord :turbulence model; magnetohydrodynamic; mhd; magnetohydrodynamic turbulence; computational fluid dynamics; continuous casting;

    Sammanfattning : Conventional one-point turbulence closures have beenextended with an additional transported scalar for modeling ofmagnetohydrodynamic (MHD) turbulence. The new scalar, α ,captures the length scale anisotropy and tendency towardstwo-dimensionality, which is characteristic feature of MHDturbulence, and allows accurate modeling of the Jouledissipation of turbulence. LÄS MER

  4. 3. Droplet growth in atmospheric turbulence : A direct numerical simulation study

    Författare :Xiang-Yu (李翔宇) Li; Gunilla Svensson; Axel Brandenburg; Wojciech Grabowski; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; cloud micro-physics; turbulence; inertial particles; DNS; condensation; collision; coalescence; atmosfärvetenskap och oceanografi; Atmospheric Sciences and Oceanography;

    Sammanfattning : This Ph.D. thesis examines the challenging problem of how turbulence affects the growth of cloud droplets in warm clouds. Droplets grow by either condensation or collision. LÄS MER

  5. 4. Turbulence Modelling of Flows Related to Wall-Cooling Applications

    Författare :Stefan Jansson; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; low-Reynolds number models; second-order-moment closures; turbulent heat transfer; two-equation models; film-cooling; near-wall models; turbulence modelling;

    Sammanfattning : Engineering flows are generally characterised by complex strain field and turbulence structure arising from a combination of shear, curvature, separation and recirculation etc. Under such flow conditions, transport by turbulent velocity fluctuations can make a significant contribution to the transport of momentum, heat and mass. LÄS MER

  7. 5. Large Eddy Simulation of Turbulent Flows in Combustor Related Geometries

    Författare :Jessica Gullbrand; Institutionen för energivetenskaper; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Mechanical engineering; Energiforskning; Energy research; Cartesian grid; high order wall treatment; SGS models; turbulence; subgrid scale models; LES; Large Eddy Simulation; akustik; vibrationer; vakuumteknik; hydraulik; vibration and acoustic engineering; Maskinteknik; vacuum technology; hydraulics;

    Sammanfattning : Numerical simulations using Large Eddy Simulation (LES) are applied to turbulent swirling flow fields. The swirling motion is often introduced into combustors to act as flame holders or enhance the mixing between species. Different turbulence models capture the swirling motion more or less accurately. LÄS MER