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Thread: Theory on lift
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Old 20th Nov 2012, 21:30
  #284 (permalink)  
PJ2
 
Join Date: Mar 2003
Location: BC
Age: 76
Posts: 2,484
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I thought I would try the "bathtub" experiment as suggested by Arvel Gentry in one of two suggested by Owain Glyndwr.

The setup is in my darkroom, using a 23" x 27" processing tray. I discovered that the best overall material to make streamlines visible on the surface of the water was pepper. I cut and bent a 4" x 6" piece of aluminum and mounted it on a make-shift handle. I filmed with a small video camera mounted on a tripod directly above the tray. The lighting was indirect flourescent.

As per Gentry's comments in the paper referenced I waited until the water was still and placed the airfoil in the water such that the leading edge would meet the oncoming fluid with a positive AoA. I drew the airfoil through the water and watched how the streamlines developed.

After a day and dozens of trials a lot of pepper had sunk and I discovered that this was even better for showing up streamlines as it wasn't just on the water surface but "3D" - about 2 inches worth. I ensured that the airfoil was as close to the tray as possible, (attempting to simulate an "infinite" airfoil) and drew it, left to right.

The experiment can be viewed here. I don't know how, yet, to link videos which are hosted on personal photo-video hosting sites like "SmugMug" such that they are visible and clickable here. Tried everything...the embedded links, the blog links, the forum links and lo, nothing works.

Microburst2002, could this, (The Anatomy of the Airplane), be the link to Darrol Stinton's book that you were looking for? This document is in pdf format - Sections 5 & 6 are relevant to the discussion.

Again, I'm not an engineer but am an interested bystander in this particular conversation which is really fascinating to a pilot. Thank you Owain Glyndwr, roulishollandais and others for a very stimulating discussion on lift, and some interesting reasons why Bernoulli, and Newton, don't make it into too many works on aerodynamics when it comes to discussing lift - not Stinton's, Gentry's or Shevell's, anyway!

Last edited by PJ2; 20th Nov 2012 at 23:50.
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