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Why is downwash on a wing not desired

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Old   November 11, 2013, 03:04
Default Why is downwash on a wing not desired
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Nick
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Hi guys,


I simulated a finite wing and sure enough there's downwash behind the wing which lowers the lift coefficient compared to a 2d wing. Something doesn't make sense to me though. If a finite wing creates more downwash, that is more fluid is pushed down behind the wing then it means there's more high momentum fluid going down compared to the 2d case. So if the wing is pushing more fluid down shouldn't the fluid push the wing up more than the 2d case (momentum balance+newton's third law)? What am I missing here.
cheers,
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Old   November 12, 2013, 17:22
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Think in 3d: rougly speaking, due to downwash air goes down along the wingspan, but up if you go away from tips (look e.g. at wingtip vorices).
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Old   November 16, 2013, 09:52
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Yes. That's a good point. Thanks.
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