The Nature of Sand

The Nature of Sand

[MUSIC PLAYING] What is this material? How do I even start? It’s all around us. And yet unlike so many
of the common materials that we get to play
with every day, the understanding of how
sand moves is just so poor. It’s one of the biggest
open questions in science. [WAVES CRASHING] [THUNDER] [THUD] Is it a solid? Is it a liquid? Or is it a gas? I think the truth of the
matter is it’s really just all of the above. [MUSIC PLAYING] When I was a student,
I would take classes where I would learn some
kind of a general governing equation that explains
how a material behaves in a general circumstance. This is true in fluids. This is true in solids–
even quantum mechanics. And I was just
astounded when I learned that there wasn’t a similar set
of equations that worked just as well for sand. I became enamored with
this idea that maybe we could come up with the answer. [MUSIC PLAYING] One of the things that we knew
was what a granular material does when it’s put into simple
shear and run to steady state. But what was weird was
we also had some data, in other cases,
other geometry, which seemed to violate the rules
that we saw in simple shearing. And I became very
intimately engaged with all of those
little violations. And in my heart, I
knew that there just had to be a simple way to
insert one extra non-local term. And if we got it
right, I had a feeling that it could solve everything. I was inspired when I came
across an approach that had been used previously
for emulsions. And when I looked at that
form, the light bulb went off. And I said, something
like that has to be behind granular materials. So I adopted the framework and
changed all of the ingredients so that it might reflect sand. And we took this model
that we had written, we tried it in every data set
we could find in the literature. And we were just
astounded when we saw that the model had
predicted all of them. [MUSIC PLAYING] Just think about all
the places that we deal with grains, and all
the ways that you could now design for those applications– pills, powders, you know,
food, raw materials. Think about all the
factories and plants that have to manipulate this
material around, and just imagine that you can now design
the equipment, optimally. We have this tool. We can actually, hopefully,
quantitatively predict. [MUSIC PLAYING]

5 thoughts on “The Nature of Sand

  1. Could these set of equations stand correct for other granular materials of same size too? or will the adhesive forces come into play to change the equations?

  2. Sand, imo behaves like a Non-Newtonian Fluid with no intramolecular adhesion under tensile loads?

  3. All mechanical engineers at one place. Join and share this group with mechanical engineers

    Join GATE/ESE (Mechanical) group on Eckovation. Group Code: 879451. Use

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