Best site I ever came across for basic intro to aerodynamics is none other (did you expect otherwise)
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You may also want to look at 2 other ways of accessing the same site:
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The site top level is related to Learning Technologies and there are many aids for teachers wanting to help others understand this material.
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From a "basic" standpoint, specifically aerodynamics, The site can't be beat.
Some of the plug-ins are Java allowing the visitor to input his choices of parameters for airfoil (shape/angle/speed) and airframe (load, size) and get reasonably good visuals of the result, allowing for developing a feel for what is happening.
But, understandably, the site allows you to grow into the subject beyond basics, although it does not get into the expert (aka, Computational Fluid Dynamics math) on the subject. But the sims do have that hidden behind the scenes built-into the Java applets.
Enjoy,
Eric