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Old Jan 26, 2013, 12:53 PM
kcaldwel is offline
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Joined Jan 2007
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They tested some wild and wonderful airfoils at Gottingen in the early days. By the time NACA started after WW1, Prandtl and crew had a lot of it figured out.

The interesting thing in the "Enigma of the Airfoil" is the divide between inviscid theory and viscosity, that exists to this day. The British spent 30 years trying to solve the general Stokes equations with viscosity, because circulation cannot be created in an inviscid fluid. The Germans just got results that worked by dividing the flow up into mostly an inviscid flow with circulation, and a tiny boundary layer where viscosity counted and the transition from laminar to turbulent occurred. They didn't worry too much that it was impossible to create circulation in a truly inviscid fluid. The results they got worked for real airfoils and 3D wings.

I'd never thought it through on those lines before.

It is also interesting that an airfoil designed strictly on Bernoulli theory looks nothing like airfoils designed to create circulation.

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Last edited by kcaldwel; Jan 26, 2013 at 03:02 PM.
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