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Old Apr 07, 2010, 04:18 PM
larryjmoore is offline
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Cool video of smoke being pulled through a propellor


I am in an instrumentation class at college. We used a high speed camera to take this video. We poured dry ice smoke over the wing then turned the propeller on. The propeller broke a light beam and started the video recording. It's interesting to look at the air being pulled through the propeller.

Smoke on Wing.avi (0 min 56 sec)


It is my 32 inch speed wing with a 400DF motor, 5.7x3 prop, 4 cell lipo, clocked at 120 MPH. In the video, the throttle was close to the lowest setting. I forget how many frames per second the video was recorded at.
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Old Apr 07, 2010, 10:09 PM
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Great video but you should have been using that lesser known variation of "Smoke On The Water" titled "Smoke Thru The Prop". Deep Purple passed on the less suitable lyrics but I understand that Weird Al Yankovic was supposed to be doing a version of the prop song....

It's interesting to see how the smoke is drawn in from a fairly wide venturi shaped segment of upstream air and how the prop stream doesn't really seem to suffer from tip vortices at all.
Old Apr 08, 2010, 07:10 AM
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Nice video indeed, how come you didn't try with higher throttle settings?
Old Apr 08, 2010, 08:18 AM
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Nice video, proves what I always thought.

Planes 'suck' themselves through the air.
Old Apr 08, 2010, 10:48 AM
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We did try it with close to full throttle, but it wasn't as interesting because all the smoke was pulled out so quick and then our dry ice couldn't produce enough to keep up. I suppose we could have sped up the camera, but then you run into lighting issues with the higher shutter speeds. The plane was already under a large halogen lamp and was very warm even after the short run.
Old Apr 08, 2010, 11:29 AM
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Notice how the smoke upstream prior to the prop was fairly undisturbed and obviously quite disturbed afterwards?

So if you're building a wind tunnel for airfoil/aerodynamic testing make sure your project goes upstream! :-)

Curtis
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Old Apr 08, 2010, 06:09 PM
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Also, it's a nice demonstration that when measuring the static thrust of a prop, the prop is "automagically" pulling through a column of moving air at near the best angle of attack. If the air column kept relatively still, a high pitched prop would probably be just stalled, but you can measure fairly high static thrust even on coarse props.I wonder if it would be possible to design a prop where reflexed blades angle themselves relative to the airflow a bit like flying wings, or like the freewing concept.
Old Apr 08, 2010, 06:59 PM
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Quote:
Originally Posted by larryjmoore View Post

It is my 32 inch speed wing with a 400DF motor, 5.7x3 prop, 4 cell lipo, clocked at 120 MPH.
What is travelling at 120 mph? The blade tips?
Old Apr 09, 2010, 02:05 AM
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The whole plane, but obviously not in the video


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