Modeling the airflow through a recorder
Thu Mar 13, 08 8:01 am
Mood: Sleepy ]So for my last project in CFD (which we get to choose), I decided to look at how the airflow inside a recorder (the flute kind) works, and how it makes sound. I'm not out of the woods yet, but I wanted to post what I have so far.
(Yes, that is a recorder, yes, I cut it in half, no, it was one of our cheap ones. Yeah, I did feel sort of bad cutting open a musical instrument. 
)
So the air from the mouthpiece hits the fipple (the angle piece at the sound hole), and initially it splits evenly across that, but then it will start to oscillate over and under it, because of a standing wave inside the recorder. We can model this with computers, so I decided to try to do that. It's not easy.
I found a german website where they already did this, so it seems like it should work. You can see their work here. (their movies are neat to watch):
http://www.bias.at/index.htm?http://www.bias.at/flutesim/index.htm
After several hours of simulation and rendering, this is what I have:
http://oregonstate.edu/~plettb/movies/CFD/CFD-Recorder.mov
http://oregonstate.edu/~plettb/movies/CFD/CFD-Recorder2.divx
(they are both the same, but the second one is larger, so it is a little clearer)
(Note that the model just shows the fluid, not the recorder.)
As you can see, it does initially split, and then it goes below, and then up. But it doesn't go back down... 
It is also very slow in going up. So that's what I need to figure out, and hopefully I will get it to oscillate.
Next week is finals. So fun.
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Cool!
