Last night Andrew and I got into a fight about fluid
dynamics. Yep. See, I had been trying to recreate this weather experiment on
cyclones and anti-cyclones:
http://www.youtube.com/watch?v=TzqvGIAWHOk,
but I couldn’t get the dynamic profile to fully develop. If you don’t have time
to click on the video, just know that the experimental set up is a can of ice
set inside a pan of rheologic fluid which is in turn set inside a larger pan.
The entire apparatus is spinning on a turntable, and at the start of the
experiment, hot water is poured into the second, larger pan. The setup is a
model of the earth: The can of ice models the cold “north pole”, and the hot water
warms up the equator (the outside edge of the inner pan).
In the video, you can see three cyclones and three
anti-cyclones form, and in between them is a continuous line which is a model
for the jet stream. But when I tried to repeat the experiment, I never got
steady cyclones or anti-cyclones; I just saw small transient cyclones form at
the “north pole.” The video is only a demonstration and therefore doesn’t give
a step-by-step methodology, so I wasn’t sure which critical thing I was
missing. One of the differences between my set up and the one in the video,
however, is that I have a Lazy Susan, and not an electric turntable, so I
couldn’t start the rotation until after I had poured in the hot water, but I
was pretty sure that wouldn’t matter. I thought I’d ask Andrew what he thought,
though. You should note that I had shown Andrew the video the night before, so
I thought he was familiar with the setup.
But Andrew said the lack of rotation would make a difference, because the hot water would make hot
spots. I blinked. What? Hot spots? In the outer pan? I stared at him, confused.
“No it wouldn’t,” I said, lamely.
“Of course it would!” he said. “The hot water would make
one part hot before it could get everywhere!”
Again, I was at a loss. Did Andrew not understand that
water… flows? “But the water doesn’t just
stay in one place!” I said. “How could it make a hot spot?”
I won’t repeat the whole argument word for word, although,
actually, I pretty much already did. We basically just kept repeating those two
statements back and forth to each other, with growing frustration. “It HAS to
create a hot spot!” “But the water doesn’t just stay still!”
Eventually, he said he couldn’t talk to me about it
anymore, because he was just too aggravated. I, however, insisted that we
continue. “I think you are not understanding something,” I said, “Because it
cannot make a hot spot! The water is being poured into an empty pan. It goes
all over the pan! It flows!”
“Wait… you’re not pouring the water into the fluid?”
Andrew asked.
OH THANK GOODNESS. So here’s what was happening. Andrew
thought I was pouring hot water into a cold fluid and failing to understand
that this would create a hot spot before the mixture had time to come to thermal
equilibrium, something that I should understand very well given my degree in
chemical engineering which is basically the study of heat transfer and fluid
flow. But to me, it seemed like Andrew was failing to understand that when you
pour water into a dish it will not stack up on top of itself but will instead flow
into the pan, something that Andrew should understand very well given that he
has POURED WATER BEFORE.
I tell you, we argued about this for a good ten minutes. And
I think we had such trouble finding different words to explain what we were
talking about, because what each of us WANTED to say was, “WHY ARE YOU BEING AN
IDIOT?”
