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1. Flying things interact with a lot more than the near air — the
interaction of the near fluid with all the rest of it is extremely
important. Pictures of vorticies, contrails and other neat things help.
I also mention the "ground effect" observed when you see water fowl
skimming across the lake. The air knows that the rest of the air is
there.
2. If something interacts with the air and goes up, some air must go
down. It's a conservation of momentum thing.
Helicopters help this discussion.
My most difficult calculation in a fluid dynamics class,
which I never quite understood, was a 2-D calculation of the momentum of
the air after interaction with an airfoil. Good luck with a 3-D
treatment.
On 12/21/2007 03:00 PM, Robert Cohen wrote in part:
Suppose you hold a wood board out the car window while driving down the
road. If the board is oriented with its plane oriented vertically, what
"causes" the pressure on the leading side to be greater than the
pressure on the trailing side?
Is your explanation of this much
different when the plane of the board is at an angle?