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Re: Bernoulli Principle, 2nd try



Viscosity seems to be a requirement for these pumping schemes and is
verboten with a Bernoulli explanation.

I have wondered how a zero-viscosity liquid would behave as it
traveled through tubes of differing sizes.

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He4 could be cooled enough to make virtually all of it be at zero viscosity.
Would the faster flow in the narrow channel still be able to
'entrain' the liquid in the middle side-tube - indicating a lower
pressure in the narrow tube?
If 'entrainment' requires viscosity AND if this He4 experiment DID
show lower pressure with the higher velocity, how would we describe
it in terms of molecular kinetics.

Well, Feynmann tells us that there ARE no discrete atoms of helium in
this situation - 'just' a macroscopic wavefunction. I wonder if any
measurements like this have been done???]



OK, ya'll, at 1:01 PM -0400 6/30/03, Edmiston, Mike wrote:
It seems to me the description given by Cliff Parker's student has some
merit.
----------
In the book "Vacuum Technology" by Andrew Guthrie,
he says "ejector pumps... depend for their pumping action on entrainment
of gas by viscous drag and by diffusion of gas into the vapor at the
boundary of a dense vapor stream."
-----------
When Clifford Parker described his student's response as "The air stream
is blowing the air particles from around the top of the ball away..."
this sounded to me like a description of the ejector process.
----------
I think Bernoulli is fine for describing incompressible fluids flowing
in pipes. Textbooks warn that Bernoulli's equation is useful for
qualitative descriptions, but Bernoulli can be grossly inaccurate
compared to actual experiments. I think this is because we extend
Bernoulli way past the boundaries for which it is valid. To be valid we
need incompressible fluid, we need zero viscosity, and we need
steady-state streamlined flow.



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Chuck Britton Education is what is left when
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(919) 416-2762 Albert Einstein, 1936