--- On Sun, 9/27/09, Robert E. Shlafer <pilotrob@webtv.net> wrote:
> "Reynolds Numbers" apply to liquids
> as far as I know (which is not that far in these respects)
> however,
Reynold's number applies to all fluids, air included. Off the top of my head at
6am - It is dimensionless, and is equal to the density times the velocity of
the fluid times effective diameter of the fuid passage divided by the kinematic
viscosity (rho*V*De/mu). For air, Reynold's number is used to calculate the
friction factor, and that's equal to .046/Re^.2 if memory serves. The
simplified form of Bernoulli in the case we are talking about is that flow:
W=density * Area * velocity. As you can see, there are common terms in each
equation, so you can manipulate them to come up with a friction factor, but
that factor will only tell you the friction per unit length, hence my "nope".
In fact, the throat reduction here makes the air behave somewhere in between a
swage and a sudden contraction. In both cases, the friction factor varies
non-linearly with the ratio of the upstream and downstream areas. You want to
keep it gradual, with a reduction angle of less
than seven degrees for the inner edge of the boundary layer of flow. Throw in
additional effects of non-uniform flow fields due to the contraction and the
effect on the vena-contracta in the venturi throat and the homogeneity of the
flow and downstream mixture suffer.
Or you could switch back to SUs.
Off to the races,
Ron
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