Re: Bernoulli's equation

[John Mallinckrodt <ajmallinckro@CSUPOMONA.EDU>]

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.  Consider the
following question:

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

            -------------
           /             \
   --------               \
                           --------

On Thu, 10 Jan 2002, Bob Sciamanda wrote:

> I would speak in terms of the buildup of "back-pressure" resulting from
> changes in the constraints imposed on the flowing fluid by the geometry of
> the pipe.
> Eg.: At a bend in the pipe, a back pressure of fluid "piling up" at the
> bend adds a "centripetal pressure" - the same thing happens to the flow of
> electrical current in a bent wire (surface charges build up).
> Similarly a diminution of pipe size will create a bottleneck - as the
> fluid tends to "pile up" at the bottleneck a back pressure is created.
> This is a very palpable phenomenon:  you can feel the increase in pressure
> in a water hose as you manually restrict the final opening.
> (I don't appreciate your wish to have  the "equipartition theorem come
> into play here" - keep it simple - it is!

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