Sökning: "Critical velocity"

Visar resultat 21 - 25 av 132 avhandlingar innehållade orden Critical velocity.

  1. 21. Molecular gas in the galaxy M83 : Its distribution, kinematics, and relation to star formation

    Författare :Andreas Andersson Lundgren; Hans Olofsson; John Whiteoak; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Molecular gas; Galaxies; Galaxies individual: M83; Star formation; Galactic dynamics; Astronomy and astrophysics; Astronomi och astrofysik;

    Sammanfattning : The barred spiral galaxy M83 (NGC5236) has been observed in the 12CO J=1–0 and J=2–1 millimetre lines with the Swedish-ESO Submillimetre Telescope (SEST). The sizes of the CO maps are 100×100, and they cover the entire optical disk. The CO emission is strongly peaked toward the nucleus. LÄS MER

  3. 22. Stabilisation of resistive-wall modes in fusion plasmas

    Författare :Demetrio Gregoratto; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; electromagnetic feedback control; Tokamak; resistive-wall mode; reversed field pinch; MHD;

    Sammanfattning : For the success of thermonuclear fusion by magnetic confinement it is important to improve on the stability limits imposed by large-scale magnetohydrodynamics (MHD) instabilities. This thesis focuses on the stabilisation of the "resistive-wall mode" (RWM), an instability which affects high-pressure tokamaks but also Reversed Field Pinches (RFP). LÄS MER

  4. 23. Studies of the rotating-disk boundary-layer flow

    Författare :Shintaro Imayama; Henrik Alfredsson; Rebecca Lingwood; Peter Thomas; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Fluid mechanics; laminar-turbulent transition; convective instability; absolute instability; secondary instability; hot-wire anemometry; Teknisk mekanik; Engineering Mechanics;

    Sammanfattning : The rotating-disk boundary layer is not only a simpler model for the study of cross-flow instability than swept-wing boundary layers but also a useful simplification of many industrial-flow applications where rotating configurations are present. For the rotating disk, it has been suggested that a local absolute instability, leading to a global instability, is responsible for the small variation in the observed laminar-turbulent transition Reynolds number however the exact nature of the transition is still not fully understood. LÄS MER

  5. 24. An experimental study on the wake behind a rectangular forebody with variable inlet conditions

    Författare :Renzo Trip; Jens Fransson; Olivier Cadot; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Bluff bodies; wake flow; asymptotic suction boundary layer; flow control;

    Sammanfattning : The wake behind a rectangular forebody with variable inlet conditions is investigated. The perforated surface of the two-dimensional rectangular forebody, with a smooth leading edge and a blunt trailing edge, allows for boundary layer modification by means of wall suction. LÄS MER

  7. 25. Shedding light on the bluff body wake instability

    Författare :Renzo Trip; Jens Fransson; Charles Williamson; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Engineering Mechanics; Teknisk mekanik;

    Sammanfattning : The flow around a vehicle, for example, results in a large resistance and can generate a complex swirl pattern behind the body of the vehicle, which can lead to strong alternating lateral forces. There is therefore a clear need for more fundamental understanding of the instability of this so-called wake region, which arises behind bluff bodies. LÄS MER