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Old 12th Jun 2011, 20:50
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Post Stall Aerodynamics

When you look at a typical Coefficient of lift curve in a publication, they always stop just past the Clmax point. See example below:

Did you ever wonder why they don't carry on further to the right? It is because past that point, it gets a lot more complicated, varying with aspect ratio, thickness ratio, and Reynolds Number.
A typical extended curve looks more like this:

The double humped curve shown above is rather typical actually. Now we have a clue where the notch in the Viper pitching moment curve comes from.

Fortunately the wind turbine industry has need of post stall airfoil performance and someone has studied the subject a bit. The following pdf file is on a slow server, so give it some time to load.

I researched this topic a bit because I was interested whether or not AF447 was likely to get stuck in a pitching moment notch of its own. Maybe so, but the THS lower aspect ratio than the wing indicates decreased likelihood of having as much of a notch as the wing might have, i.e. more nearly linear performance.
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