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On Thu, 26 Aug 1999, Richard Tarara wrote:
There is NO upwash without the wing (in motion) being present.
Obviously!
The upwash
HAS to be caused by the wing doing _something_ to the air.
Hi Rich! Right. However, if the wing created the chordwise circulation
in the distant past, then, in a nonviscous simplified model, that
circulation continues conceivably forever. That circulation is similar to
a coasting wheel. It inherently contains this idea: equal amounts of
upwash and downwash. If we think of the region of the chordwise
circulation as being a flywheel, we would state it like this: "one bit of
the flywheel accelerates another bit of the flywheel, and the forces
between them sum to zero and do not produce a net force upon the axel of
the flywheel." If we describe the air surrounding the wing, we would say
"one air-parcel in the pattern of chordwise circulation accelerates
another parcel of the same pattern of circulation, but the forces between
them sum to zero and do not produce a net lifting force upon the airfoil
as a whole."
Define this
process _exactly_ and perhaps some of the conflicts will be resolved.
That's the problem because the definition is different in a 2D model than
in a 3D model. In a 3D model, those darned wake-vortices behind the wing
make the downwash NOT behave as part of a spinning flywheel of chordwise
circulating air. As a result, a 2D crossection of a 3D airflow does NOT
resemble the air-flow surrounding a traditional "infinite wing" 2D flow
simulation. This issue causes Bernoulli-ists and Newton-ists to
constantly be at each other's throats.
To me it looks simple: dump the 2D model, and declare that it's just too
simple to explain the flight of a 3D craft. Use a 3D fluid flow
simulator, and maybe simplify things by investigating 2D flow-pattern
crossections of the complete 3D flow pattern. The staunch Bernoulli-ists
say "No, we will not do this", but they do not give any good reason for
their stance, and do not show me why my assertion is flawed. I say this:
(and have said it for years): "By simplifying the 3D airflow and placing
it into a 2D world, the loss of degrees-of-freedom has profoundly changed
the physics of flight, and as a result, a 2D flow simulation does not at
all describe the physics of a 3D wing in level flight at high altitude."
The Bernoulli-ists say "No, you're wrong", but do not show me why my
assertion is faulty.