Saturday, February 22, 2014

How Dry Ice Saved my Saturday

The past month, on Saturdays, I have been teaching elementary kids about fluid mechanics.  I had grand plans for this course, plans that included building a wind tunnel so that we could do some experiments.  How hard can it be to build a wind tunnel, I thought.  I practically got a PhD in lab repair.  

But then life happened due to a series of events.  Less than a week before the last class, no tunnel had been built.  I was determined, though.  This was going to happen. 

I worked on this tunnel all week long, putting in several hours each day to build the requisite parts of the tunnel.  By Friday, all I had left was to figure out the visualization of the flow.  

The result was kind of a mess.  Incense smoke?  Yeah, it made an ashy mess in my kitchen and left my roommate with a headache from the fumes.  It had looked so simple on the NASA website and so straightforward on the wind tunnel in Japan.  Why wasn't it working for me?  

"Time's running out," I thought last night around 9 pm.  "Can I appease the kids with a non-working wind tunnel that was made, literally, from cardboard and duct tape?"  It was almost laughable, except that piece of cardboard held together with duct tape had taken my entire week!   

I convinced my roommate to let me try one more time, with the tunnel exhausting out the window so that the incense didn't overwhelm the apartment.  As we lit several incense sticks and held them up, a few friends happened by our open window.

"Whoa!  What are you doing?"
"Come see!"  We invited them in.  "We're trying to figure out how to make this wind tunnel work."  

With four heads put together, we figured out that reducing the mass flow rate helped make the smoke more visible.  However, looking at the ashy fragrant mess, I wondered how this would work on a practical level in the classroom.  

"Why not try dry ice?"  One friend suggested.  Together, we trekked over to the local supermarket and bought a block of dry ice to try it out.  (Apparently, it's that easy - if you're over 18, that is.)  

It worked, like a charm.  The wind tunnel ran.  The class was a success.  I went away, rejoicing.
Artistic shot with Annie's foot.  
(The multi-colored part is the honeycomb made of over 1000, 1 inch pieces of straw taped together)

1 comment:

  1. That was the sweetest cardboard wind-tunnel I have ever seen. It was a noble sacrifice to gift that to future generations of child-physicists. I'm still a little sad that I never got to see how it worked with the dry ice.