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# O.K., How Do Wings REALLY Work?

William J. Beaty 2003

## UNDER CONSTRUCTION! very!

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A ring-vortex (or a cylindrical vortex-pair) acts like a single object.
The
air "thinks" that a ring-vortex is a sphere.  The moving ring carries the
air in the ring along, but it also carries along the air in the "donut
hole," and the combination forms a moving air-ball.  Yet since this
"sphere" contains internal flow, the surface drag of the sphere
surrounding a vortex-ring is
insignificant when compared to the drag on a real sphere.  Throw a ball
and you get air friction, but throw a vortex-ring and you get almost
none.  BRAINSTORM!
Make a motor-spun flettner wing aircraft.  Replace each normal wing with
a
pair of cylinders, one above and one below.  WHen this airplane moves
forward, the cylinders will counterrotate, and the drag will be extremely
small.   This resembles the "smoke-ring blimp" discussed elsewhere.  OK
now tilt the two cylinders so they have an "angle of attack."  They will
spin differently, with the upper cylinder going faster.  Add the rotations
together and you don't get zero anymore:  the wing has become a flettner
rotor.  The main difference is that the drag is tiny.  DOUBLE-ROTOR
FLETTNER CRAFT.  They need no motors to drive the spinning cylinders.  The
air alone does it.

Water or Air: no important difference Analyze wings under water
or in air.  The results, the shape of the flow patterns, will be the
same.  According to the physics of aerodynamics, air is not "special,"
and underwater wings are just like normal aircraft wings.  The physics
applies to all fluids including both gases and liquids.  So, if a theory
of flight relies on the significant compressibilty of air, then that
theory is wrong, since wings work just fine when flying under water.  A
proper theory must explain all wings, rudders, propellors, etc, and not
just the ones flying in air.

Pressure differences linked to flow deflections The solid parts
of wings, rudders, and propellors deflect the moving air so it flows at
an angle. The deflected air tries to leave a pocket to one side and an
excess buildup on the other side. Instead of creating a vaccum and a
high-densiy zone, the gas or liquid moves.  It rushes into the vacuum in
just such a way that the fluid density never changes.  The fluid slows
down and avoids the "buildup" in just such a way that the fluid density
never changes.  But the pressures certainly change!  The fast flow is
associated with a low pressure, and the slowed flow is associated with a
high pressure.  No "vacuum pockets" in the air, but there certainly are
regions of different flows and different pressure.

Moving ball:  air moves backwards while ball moves forwards.
Moving air across ball: air slows down ahead, speeds up behind.
slow air ahead: high pressure retards ball
slow air behind: high pressure drives ball ahead
pressures cancel!
fast air above: low pressure lifts ball
fast air behind: low pressure drives ball down
pressures cancel! Streamline the ball, and the pressures above and below
it remain low. Tilt the streamlined ball or "airfoil", and the pressures
change.  But the several different pressures are extremely misleading!
The streamlined ball supports a complicated pressure pattern even when NOT
tilted.  Conclusion: to understand lift, analyze a tilted flat plate
instead of an airfoil.  That will teach you about the lifting force alone
because it strips away the crazy pressure fields which appear around
airfoils.

Why use 'airfoil' shape at all?
Why are airfoils bulbous in front and pointy in back?  Well, we should ask
what happens if the airfoil is reversed?  It turn out to work just fine,
but only as long as no flow-detachment or discontinuous flows appear.
The front of a train can be sharp and pointy.  The same goes for rockets.
However, the tiniest tilt will cause a massive "stall" and a huge drag
force.  When a pointy airfoil is tilted, the air isn't able to make it
around the sharp leading edge.  Even a tiny tilt will trigger a massive
stall.  But put the point in the back and make the front edge bulbous, and
things work great.  The bulbous front edge prevents stalls. Therefore we
must conclude that airfoil "streamlining" isn't there to prevent viscous
drag.  Instead it's there to prevent the 2nd-order drag whcih comes from
"stall" and turbulent stirring of the air.

Trailing edge MUST be sharp Now lets look at the rear half of the
reversed airfoil.  The bulbous rear has a very interesting effect: when
the airfoil is tilted, it DOESN'T DEFLECT THE AIR.  Instead the air flows
straight back from the bulbous part.  This makes some sense:  when the
airfoil had a sharp trailing edge, inertia forced the upper/lower flows to
leave the edge in whatever direction the edge was pointing.  But without
that sharp oint, the upper/lower flows collide head on, and they can
decide on their own the anle of departure.  WIthout that sharp edge to
guide them, the air flows ignore the tilt angle.  (Well, if the air was to
flow MUCH faster, then the upper/lower flows would again obey the tilt
angle, but only because the flows "detach" and the bulbous part becomes
shrouded in dead air which mimics a sharp trailing edge.)

Why is this not in textbooks?

Aerodynamicists are misled by a widespread textbook error: the classic
analysis of inviscid irrotational flow around an infinite cylinder and
around an infinite cylinder which is spinning.  This analysis tells much
about the lifting force, but it hs an unfortunate feature: an infinite
flow field which applies forces to distant surfaces. In the real world we
have no infinite cylinders, and the flow field around a finite cylinder
creates pressures which drop off differently than those around an infinite
one.  A finite cylinder only applies forces to distant surfaces if those
surfaces are within a few cylinder-lengths distance.  Maybe an electrical
analogy will help.  Look at a single electron.  It's field extends to
infinity, and it attracts distant charges.  But look at a DIPOLE (an
electron and positron adjacent.)  The dipole field extends to infinitey,
but it drops off so fast that the dipole only interacts with charges which
are within a few dipole-separations distant.  Another: AC in an infinite
wire will induce the same current in an infinite metal plate no matter how
far that plate is from the wire, but a WIRE RING is different.
Alternating Current in a wire ring will induce smaller and smaller
currents in an infinite plate as the ring is moved away from the plate. In
other words, aerodynamics undergrads have been studying the "Ground
effect" without realizing it.  They thought they were explaining how wings
work, but instead they were explaining how wings interact with the nearby
ground during very low altitude flight.  This is a major mistake, and it
has repercussions which resonate through all of aerodynamics science.
The mistake is perfectly sensible: it is easier to analyze an infinite
wire than to analyze a coil.  An infinite wire gives a 2D field
distribution which is instantly grasped by students, while coils give 3D
fields which are m uch more difficult to understand.  But the force-pair
between an infinite wire and an infinite plane is constant regardless of
distance betwen them.  Flows around infinite wings explain "venturi
effect" and ground-effect flight.  They do not explain how airplanes work.

Hey, the smoketrail pattern around an infinite cylinder displays viscous
interaction, and the speed gain of air passing by the cylinder does not
equal the speed loss of air approaching and receding:

(animation from

http://www.av8n.com/irro

I need an animation of TWO COUNTERROTATING CYLINDERS so I can see how the
fluid outside the cylinders behaves.

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