Advertisement

Wall Effects for the Free Rise of Solid Spheres in Moderately Viscous Liquids

Authors

  • Kevin H. Dewsbury,

    1. Department of Chemical and Biochemical Engineering The University of Western Ontario, London, ON N6A 5B9, Canada
    Search for more papers by this author
  • Aristotelis Tzounakos,

    1. Department of Chemical and Biochemical Engineering The University of Western Ontario, London, ON N6A 5B9, Canada
    Search for more papers by this author
  • Dimitre G. Karamanev,

    Corresponding author
    1. Department of Chemical and Biochemical Engineering The University of Western Ontario, London, ON N6A 5B9, Canada
    • Department of Chemical and Biochemical Engineering The University of Western Ontario, London, ON N6A 5B9, Canada
    Search for more papers by this author
  • Argyrios Margaritis

    1. Department of Chemical and Biochemical Engineering The University of Western Ontario, London, ON N6A 5B9, Canada
    Search for more papers by this author

Abstract

For the first time ever, the influence of wall effects on the free rise of a buoyant solid sphere in a square column in a non-Newtonian (pseudoplastic) fluid was determined. It was found that in most cases, as the column width decreased, the terminal rise velocity of the sphere would decrease as well. It was also discovered that wall effects could change the rising sphere trajectory. Spheres that displayed a spiraling trajectory in larger columns would display a more linear trajectory in smaller columns. Occasionally, due to this change in trajectory, the solid sphere terminal velocity would increase as the column width decreased. This phenomenon (the positive wall effect) has not been reported for falling spheres in Newtonian or non-Newtonian fluids.

Abstract

L'influence des effets de paroi sur l'ascension libre d'une sphère solide flottante dans une colonne carrée dans un fluide non newtonien (pseudoplastique) a été déterminée pour la première fois. On a trouvé que dans la plupart de cas, si l'on diminue la largeur de la colonne, la vitess d'ascension terminale de la sphère diminue également. On a également découvert que les effects de paroi peuvent changer la trajectoire de la sphèremontante. Les sphères montrant un trajectoire en spirale dans les colonnes larges montrent une trajectoire plus linéaire dans les petites colonnes. Occasionnellement, en raison de ce changement de trajectoire, la vitess terminale de la sphère solide peut augmenter alors que la largeur de la colonne diminue. Ce phénomène (l'effect de paroi positif) n'est pas signalé pour des sphères tombantes dans des fluides newtoniens et non newtoniens.

Ancillary