68th Annual Meeting of the APS Division of Fluid Dynamics (November 22, 2015 — November 24, 2015)

V0106: Strangely Stable Sphere Stacking

  • Piyush Singh, University of Illinois at Urbana-Champaign
  • Jason Lee, University of Illinois at Urbana-Champaign
  • Jonathan Freund, University of Illinois at Urbana-Champaign
  • Randy Ewoldt, University of Illinois at Urbana-Champaign
DOI: https://doi.org/10.1103/APS.DFD.2015.GFM.V0106

We observe a new phenomenon whereby spheres sediment and form a single, stable vertical stack in a yield-stress fluid. Individually, the spheres settle to the bottom, since the yield stress is insufficient to suspend a single sphere. However, cooperative effects result in surprisingly stable stacking. The fluid is composed of water with a small amount of additive (0.15 wt% of polymer microgel particles, Neutragel DA). This class of fluids, known as yield-stress fluids, are effectively solid at low stress though flow at high stress. Similar non-Newtonian behavior is used in everyday products like toothpaste and hand sanitizer, as well as in technological applications such as fire suppression and additive manufacturing. With this video, we aim to spark curiosity and interest into the intriguing world of yield-stress fluids in particular and non-Newtonian fluids in general.

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