zero lift and induced drag
zero lift and induced drag
(OP)
hi. this may seem a stupid question, but i have gone through a couple of books now (dubs, hoerner, schlichting, crowe)and i still don't quite get it. according to the basic formula, induced drag coefficient of a wing is proportional to lift coefficient squared:
C(draginduced) = C(lift)^2 / Pi*aspectratio
therefore, if a wing generates zero lift it must also generate zero induced drag. but the literature seems to be quite vague about this. schlichting says induced drag occurs with all finite wing spans. but he also states that "within the range of small lift coefficients, the drag of airfoil sections is predominantly frictional..."(fluid-dynamic drag, 1969).
aleyev states that induced drag is "significant when there is hydrodynamical lift" (nekton, 1977).
but they don't clearly say that zero equals zero induced drag.
could anybody help me understand this or at least point me in the general direction of literature that would help me?
C(draginduced) = C(lift)^2 / Pi*aspectratio
therefore, if a wing generates zero lift it must also generate zero induced drag. but the literature seems to be quite vague about this. schlichting says induced drag occurs with all finite wing spans. but he also states that "within the range of small lift coefficients, the drag of airfoil sections is predominantly frictional..."(fluid-dynamic drag, 1969).
aleyev states that induced drag is "significant when there is hydrodynamical lift" (nekton, 1977).
but they don't clearly say that zero equals zero induced drag.
could anybody help me understand this or at least point me in the general direction of literature that would help me?





RE: zero lift and induced drag
The induced drag is more accurately called "lift induced drag". You are correct that at zero lift (cl = 0), the lift induced drag would be zero. But the total drag will not be zero.
Also, the formula for lift induced drag is more accurately:
Cd(lift induced) = cl^2/(Pi * e * AR), where:
cl - coeff. of lift
Pi = 3.14159
e - Oswald's efficiency factor
AR - Aspect Ratio.
I hope this helps.
-Amin
RE: zero lift and induced drag
RE: zero lift and induced drag
RE: zero lift and induced drag
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RE: zero lift and induced drag
RE: zero lift and induced drag
RE: zero lift and induced drag
For an unviscid flow, you will obtain zero drag for a zero lift finite wing.
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