Re: How Important Is Cross-section Shape Of Wing?

Date:         16 May 2001 17:45:15 
From:         "Johan Eertink" <eertink@nlr.nl>
Organization: National Aerospace Laboratory NLR
References:   1 2
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For what I've learned in aerodynamics classes, the vortex is a by-product of
the lift producing characteristics of the wing: High pressure underneath,
low(er) pressure on top => At the wingtip, the air flows from underneath to
top, thus producing a vortex as the aircraft moves forward.
This is basically an unwanted process, since you loose energy that you want
to use to lift the aircraft. The "winglets" you find on many modern
airliners are helpful to minimise this.

As for Bernouilli: This is not fiction (as confirmed in the webpage you
refer to).  B's law only states that moving air has lower pressure when it
moves faster. No doubt about that. The question is about how to make air
move faster over the top of a wing. This is achieved by placing the wing at
an angle of attack w.r.t. the airflow. Rounding the nose and pointing the
trailing edge helps the flow in staying attached to the wing.

Johan

"JWizardC" <jwizardc@aol.com> wrote in message
news:airliners.2001.162@ditka.Chicago.COM...
> Okay, here's another simian torquer (monkey wrench): When I got to
advanced
> aero design classes, I learned that Bernoulli is mostly a convient fiction
to
> help explain a mind numbingly difficult truth. In actuality, as a
wing-shaped
> object begins to move forward in a fluid (like air), an amazing phenomenon
> takes place. A vortex begins to form behind the wing, creating a partial
> suction, which pulls more air over the top of the wing -- here's the hard
part
> -- from underneath it!
> Wander over to http://www.geocities.com/galemcraig/ for a discussion far
better
> than I can provide here.
> TheFNG