NARRATOR: This video supported by Udacity.
OK.
Can you just turn it on?
Should we wear like goggles in case, sand-- oh yeah,
you got the button behind you.
I don't think it's going to go anywhere.
You don't think so?
No.
Can I go for it?
Yeah.
[YELL]
You said it wasn't going to go anywhere.
[LAUGHS]
You lied.
I trusted you.
You were leaning over it.
It couldn't have been any better.
I'm pretty sure they put sand in toothpaste, so
how bad could it be?
Hey, I'm Diana.
You're watching "Physics Girl," and I am here
with William Osman.
I drove up to Ventura to meet with William
and his cameraman, John, who you may know
from such works of art as--
Sandwich Vin Diesel.
DIANNA COWERN: Yeah, sandwich Vin Diesel on YouTube.
WILLIAM OSMAN: I think that's it.
No one else knows anything else.
Well you've got this-- what is it called?
Retina Smelter.
Retina Smelter 9000.
Yeah.
And what I wanted to do, I saw this GIF
on the front page of Reddit.
And it was turning sand into liquid
by bubbling air through it.
Had you seen it?
WILLIAM OSMAN: I did, yeah.
I actually had.
DIANNA COWERN: Yeah.
I thought it was going to be a lot easier than it has been,
to be honest.
Yep.
I ate sand.
Oh, my god.
Oh.
OK.
That, it didn't, like, work at all.
What do we do?
[MUSIC PLAYING]
WILLIAM OSMAN: Oh, wow.
DIANNA COWERN: Oh, yeah.
WILLIAM OSMAN: Minus the fact that it's
going literally everywhere.
DIANNA COWERN: OK, first problem, too much air.
It took us much longer than we should admit to eventually
figure this out, and switch from using a shop
vac to using an air compressor.
But in the meantime, the sand quality problem.
[VACUUM]
Who knew all sand from hardware stores is wet in Ventura?
Now this is so much better.
There's not much on the internet for how
to do something like this, besides especially
academic papers.
So we looked really closely at Google Images.
And noticed that the sand grains are particularly fine.
Get it?
Particularly, like particle, get it?
No?
OK.
So I order some sandblasting glass beads like these really,
really, really tiny spherical glass beads
from McMaster, which had the added
bonus of acting like water droplets
when light shines on them.
Because they're pretty uniform in shape and size.
And so they reflect and disperse light to make a rainbow.
I love rainbows.
Our first setup was a Tupperware container
with a wooden box we had made with a laser cutter,
with a bunch of holes cut in the top by the Retina Smelter 9000.
And the holes were an attempt to get the air from the input
into the wooden box to go uniformly up through the sand.
It didn't work.
[VACUUM]
The problem was once the air finds a path through the sand,
it makes that the preferred path.
It's like a river cutting a valley through a mountain.
Eventually all the water will follow that path.
So we had to make it so that the air would
want to follow all paths equally, like a mountain
that you can't cut a valley into.
So over the weekend, William made a new setup.
Thanks, William.
With a bigger wooden box as the lower chamber
that gets pressurized by the air input,
and then we used a cloth instead of all those little holes
to equally distribute the air pressure.
And then our main sand chamber was a white plastic bucket.
Here's how that went.
WILLIAM OSMAN: Ready?
DIANNA COWERN: Mm-hmm.
Ah-ha!
That's awesome.
WILLIAM OSMAN: That's really cool.
DIANNA COWERN: So that's cool.
So I've really got some--
I mean it's like buoyant.
The problem I think here is that the t-shirt material we used
was too stretchy.
So it bulged up in one place.
And that became the preferred path of the air like,
the river valley.
So we tried a thicker material from a tablecloth
and stretched it really taut over the ring and glued it.
And-- Yes!
It worked.
This is so exciting.
Oh, we blew through that part.
For a little bit.
[MUSIC PLAYING]
The reason that this strange phenomenon
occurs that sand can act like a liquid
and you can stir it and float things,
is that we're causing fluidization.
Fluidization happens when you bubble fluids like air
through solid particles, like sand.
I know you may be thinking, but air is not a fluid.
Well, in the world of fluid dynamics, gases are fluids.
They flow like fluids.
So the fluid, the air, acts to decrease friction
between the sand grains because it keeps them more separated,
which is important.
And of course, there's not much friction
between the fluid and the particles.
So with this decreased friction, the sand can act like a liquid.
And as you increase the amount of gas
you're bubbling up through, the particles eventually
come to an equilibrium between a force
upward by the gas and a force downward by gravity.
And the particles become sustained in the flow.
It's like they're floating.
And then they form a nice soft bed,
which is why engineers call this a fluidized bed.
Now if you increase the gas velocity,
the particles will no longer form this nice bed
and they'll be carried upward by the gas flow.
[VACUUM]
[YELL]
Fluidization is incredibly common in industry.
For example, it's used to control
the temperature of combustion.
So if you want things to burn at a lower temperature,
because when they burn at a higher temperature
you can produce more harmful pollutants.
NOx and SOx.
So bubbling up a cooler gas between your solid fuel
particles will cause them to burn at a lower temperature.
Fluidization is also used in the food industry,
like if you want to cool down something particulate really
fast, like peas or corn, you bubble cool air up
through them.
And an everyday example of fluidization
is those hot air popcorn cookers where you bubble up hot air,
and the popcorn kernels look like they're boiling.
Anyways, this was a super fun project to fail at.
Somehow when I do these experiments,
I always end up unscathed.
You shouldn't work with me.
It's not good for your health.
But thanks anyways to William and John
for making this happen.
Check out their channel.
It's called William Osman.
It's hilarious and informative.
I'll put a link in the description.
And speaking of failure, maybe if we had had an online course
about how to make a fluidized bed,
we wouldn't have failed so hard.
So, smooth segue, I'd like to thank Udacity
for supporting this video and PBS Digital Studios.
Udacity is committed to teaching the cutting-edge Silicon Valley
skills for the jobs of tomorrow, with Nanodegree programs
in web, digital marketing, self-driving cars, data,
deep learning, and artificial intelligence.
You can advance your career with a Nanodegree credential that's
recognized by the world's most innovative companies.
To receive a limited-time discount,
go to udacity.com/physics-girl.
And maybe put in a request for a fluidized bed course.
OK.
Thanks for watching.
And happy physics-ing.
[MUSIC PLAYING]