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Re: [Phys-l] question about Bernoulli



On 11/22/2010 10:08 PM, John Mallinckrodt wrote:
On Nov 22, 2010, at 7:52 PM, John Denker wrote:
On 11/21/2010 06:22 PM, John Mallinckrodt wrote:
/snip/ except in boring
cases, steady flows are only steady in *one* reference frame.
/snip/ two semi-infinite airmasses, one to the left of the XZ plane
and one to the right. They are sliding past each other. This
is a steady flow.
-- In some frame, airmass A is moving in the +X direction while
airmass B is moving in the -X direction.
-- In another frame, airmass A is moving while airmass B is
stationary.
-- In yet another frame, airmass A is stationary while airmass
B is moving.
Indeed, that is an instance of what I called a "boring" steady flow.

So, in accordance with Bernoulli's principle, which airmass has
the lower pressure?

Hmmm...I haven't been paying much attention: which boring
air mass has the lower pressure?
Both - at the interface.
When the reference frame moves parallel to this interface, what changes?
Not much.
This region of interface between two parcels of air at different speeds is
interesting because the appreciable angular momentum which this situation
implies, leads to tornadic vortices, or on a smaller scale, wing tip vortices.

Brian W