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Re: Bernoulli Principle, 2nd try



Gary Turner wrote:



There may also be a problem with the assumptions when considered at a
molecular level. If you have purely laminar flow, there is no room for
perpendicular velocity components in the flow field. If you have non-
viscous flow, there are no boundary layers otside the main flow field to
house those perpendicular components, so where do the wall-fluid
collisions come from in the first place? If they aren't there, what is to
stop a fluid in an adjacent static reservoir from being bumped into the
laminar flow by the non-laminar motion behind it?

I am not sure I correctly understand your argument but let me present an
overidealized picture of the surface of the train's or submarine's wall which
is in relative movement and therefore in friction with the adjacent fluid:

___I___I___I___I___I___

There are small perpendicular plates which "sweep" fluid molecules in the
direction of the relative movement of the train or submarine. Clearly,
sweeping depletes the area adjacent to the wall of fluid molecules and for
that reason the pressure drops.

Pentcho