reynolds number

First, thanks to Oliver for a much better explanation.


It's not about the size of a molecule, but how they interact
with each other and surfaces at different energy levels.



These links are a few animations and film clips that depict air flow
and increasingly higher Reynolds numbers.



This first one is at VERY LOW Reynolds and displays a nearly Newtonian
reaction. I suspect that if people think about air flow, this is how
they would expect it to behave.
http://www.youtube.com/watch?v=rbMx2...eature=related



But kick the velocity up to flying speeds and see what actually happens...
http://www.youtube.com/watch?v=A4taH...eature=related
http://www.youtube.com/watch?v=vQHXI...eature=related



Transonic range...
http://www.youtube.com/watch?v=ZMEQJhiebu4
And a standing shock wave on a sub sonic airliner wing!
http://www.youtube.com/watch?v=duCHF...eature=related



Actual photographs of supersonic shock waves (an interesting film
about supersonic flight too)
http://www.youtube.com/watch?v=atItR...eature=related



So, what about an actual airfoil?
Department of Engineering, University of Cambridge, multimedia video from
Physics Education, 2003, by Holger Babinsky.
The smoke tunnel really lays it out clearly.
And the pulsed smoke flow can start a lot of arguments!
http://www.youtube.com/watch?v=6UlsA...eature=related



This one I like because it shows a "long bubble" developing on the top
surface of the wing.
It's not what they were after, but it clearly shows the bubble development.
http://www.youtube.com/watch?v=J-xxC...eature=related