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Reproduction of the phenomenon with sand

  1. Sep 27, 2011 #1
    Hello, guys, Im new here. I'm wondering, what kind of sand should I use to reproduce this phenomenon: http://www.youtube.com/watch?v=X7LpmE9hl-c&feature=related
    I've tried several kinds of sand, but the phenomenon hasn't observed.
    What density should sand has? What is the fraction (diametr) of sand?
    Thank you.
    PS: I dont asking about origins of this effect. Just want to reproduce it.
     
  2. jcsd
  3. Sep 27, 2011 #2
    You want the sand to behave as much like an ideal fluid as possible. Therefore, I would imagine you want the density of the sand to be as low as possible. You would also want the grains to be as small, and as uniform, as possible. You could accomplish both of these by running the sand through a ball mill.

    You also want the ball/projectile to be as dense as possible. Copper and iron are good choices.
     
  4. Sep 28, 2011 #3
    Thx for reply.
    I've tried quartz sand with diameter of grains 0,1 mm, but it behaves more like a flour, such as 0,2 mm. With grains sized 0,63 mm the phenomenon isn't observed, too. With further increasing the phenomenon isn't observed. I decided to swap my attempts with quartz sand to attempts with a river sand. It was rather wet, so I've dried it with an oven. Then I filtered it to size ~3/4 mm (as it looks). It feels more soft then quartz and the ball goes in it (not deep), but the phenomenon doesn't observes. Ideas?
     
  5. Sep 28, 2011 #4

    Borek

    User Avatar

    Staff: Mentor

    Have you tried to google authors? With names and university given in the video it shouldn't be difficult.

    Have you tried different ball sizes? Different drop heights? Could be it is a matter of correct selection of several parameters that play together. Something like having Reynolds number in the correct range (no, I am not saying it is about Reynolds number, that's just a lame analogy).
     
  6. Sep 28, 2011 #5
    Take a look at this article:

    http://arxiv.org/abs/cond-mat/0406368" [Broken]

    Details about the sand and steel ball are given in the first paragraph. Sand grains are around 40micrometers.
     
    Last edited by a moderator: May 5, 2017
  7. Sep 28, 2011 #6
    Thank u.
    "Therefore, in order to prepare a welldefined
    initial state, we decompactify and homogenize
    extremely fine sand (average grain-size of about 40μm;
    grains are non-spherical) by blowing air through it via
    a perforated bottom plate. The height of the sand bed
    above the bottom plate is typically 25-40cm. The air is
    slowly turned off before the experiments and the grains
    are left to settle in an extremely loose packing with the
    force-chains either broken or substantially weakened. We
    call this a “fluid-like” state" - for those, who interested in it, too.
     
  8. Sep 28, 2011 #7
    I'll tell u, if my experiments will go on well.
     
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