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Re: Bernoulli's equation

At 04:39 PM 1/10/02, Bob Sciamanda responded to John Mallinckrodt's note in
this way::

<ajmallinckro@CSUPOMONA.EDU> Thursday, January 10,
2002 3:49 PM in re Bernoulli's equation

> I don't think one ought to associate the concept of "back
> pressure" with Bernoulli's equation since it requires
> distinguishing between "upstream" and "downstream", something
> Bernoulli's equation manifestly does not do.



Huh? Doesn't Bernoulli's equation deal with laminar fluid flow? There is a
v there, a flow velocity. I don't understand your objection.



>Consider the following question:
>
> An ideal fluid flows through the pipe shown below. Where is the
> pressure highest and why?
> --------
> -------- /
> \ /
> -------------
>
> -------------
> / \
> -------- \
> --------
>



If I read correctly, we have a pipe narrowing followed by a pipe
enlarging. At each junction there is a pressure gradient - a pressure
drop at the first junction (where the fluid speeds up), and a pressure
rise at the second junction (where the fluid slows down). I assume a left
to right flow direction in your diagram.
What's the problem?

Bob Sciamanda (W3NLV)


In some practical cases of interest, it is that second junction that is
the difficulty.
There may well be little or no pressure recovery. People have to work at it
to take that pressure back instead of squandering it on turbulence.
A smooth, slowly increasing divergent cone is the name of that game.
A laminar flow is helpful.



Brian Whatcott
Altus OK Eureka!