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Theoretical question (aspect ratio)

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Birdman100

Well-Known Member
Joined
Jun 12, 2013
Messages
807
Location
Novi Sad, Vojvodina
Well known formula for induced drag coeffic is Cdi=CL^2/(AR*PI*e).
Formula for AR is AR=b^2/A (b-span, A-wing area).

What confuses me, is that these formulas (especially the latter) give same results for, what I consider as aerodynamic different cases.

Picture will help:
123.jpg
All tree cases have the same wing area and the same chord wing. Actually all tree wings have the same half wing span. My first thinking was that these tree wings are aerodynamically equivalent. (I am talking about wings here only, parasite drag, interference and other are ignored). But, according to formula all tree wings have different AR (because of different span), and thus different induced drags. Is it possible that adding body with same wing geometry can lower induced drag?

My second thought is that it is possible. Putting any body between wing halves would take some load on itself (the wing pressure propagates under fuselage) so I guess that would be the reason for lower wing load thus decreasing induced drag. What do you think?
 
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