WEBVTT

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- Okay, so what I have here

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^is a little tabletop demonstration of this

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^granular sorting phenomena

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as it applies to the unexploded ordnance problem.

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So, what we have here is a little acrylic box

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and it's half filled with sand

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and the sand is saturated with water.

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You see a little white ball down here at the bottom,

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that's actually Delrin plastic.

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Sitting proud up at the top is a steel ball,

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and of course it's sand in the middle here.

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Now, when you talk about the density

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of these different materials,

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Delrin is roughly half the density of sand,

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and the steel ball is more than twice the density of sand.

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And so, what I'm going to do is

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I'm gonna take this container and I'm gonna start

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shaking it back and forth on the tabletop here.

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What I'm simulating is what waves would be doing

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to the sea floor as they pass overhead

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and rework the bottom.

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And so what you're gonna see immediately is that

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the steel ball, which is more than twice as dense as

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the sand, is immediately gonna bury.

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And you notice the plastic ball

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hasn't really moved anywhere yet.

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And so I haven't been shaking it very hard.

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So, I'm gonna shake it a little harder now,

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I'm gonna make the waves bigger, alright,

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so the waves are starting to break now.

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(mumbles)

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What you see is that the plastic ball rises to the top

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and the steel ball continues to sink.

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And this granular buoyancy phenomena is

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an irreversible process, so no matter

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how hard I keep shaking this--

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(box scraping against the table)

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- -that plastic ball will never go back down and

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the steel ball will never come back up to the top.

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Now of course, I have a magnet that I use

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to bring the steel ball back up to the top

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to reset the demonstration.

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But this is the granular sorting phenomena

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that we think explains a large part of the

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Munitions Mobility Problem.