Unformatted text preview: Fall 2003 Uniﬁed Engineering
Fluids Problem F22 F22. A long rectangular wing has span b and chord c, and hence the wing area is S = bc.
a) The wing airfoil has certain lift and drag coeﬃcients c and cd which are constant across
the span. Determine how these relate to the wing’s overall CL and CD .
(Hint: Determine L and D , then get L and D , then from these determine CL and CD ).
The wing airfoil has a drag p olar which can be approximated by
cd 0.01 + 0.015 c3 in the range c = 0.1 . . . 1.2. The propulsive power P needed to overcome drag D at ﬂight
speed V∞ is given by
P = D V∞ P cl
1.0 ? 0.5 0.0 0.01 0.02 cd V b) Determine the form of the P (V∞ ) relation in level ﬂight, and plot it for the range c =
0.1 . . . 1.2. Any constant multiplicative factors on the P and V∞ axes are not important –
only the shape of the curve is of interest. Hint: Simplest approach is to plot P (c ) versus
V (c ) with c as a dummy parameter.
(Note: Using only the airfoil’s cd ignores other contributions such as induced drag, which
b ecome especially signiﬁcant at low ﬂight speeds!) ...
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 Fall '05
 MarkDrela
 Aerodynamics, Wing, Lift, wing airfoil, long rectangular wing

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