Page 267 - Aerodynamics for Engineering Students

250 Aerodynamics for Engineering Students

-
-
Incidence
Incidence
m
c
0
c
.- .-
0
c
Lc - -
e
e
Lc
P
Fig. 5.34 Lift-versus-incidence curve for an aerofoil section of a certain profile, working two-dimensionally
and working in a flow regime influenced by end effects, i.e. working at some point along the span of
a finite lifting wing

a certain profile working two-dimensionally and working in a flow regime influenced
by end effects, i.e. working at some point along the span of a finite lifting wing.
Assuming that both curves are linear over the range considered, i.e. the working
range, and that under both flow regimes the zero-lift incidence is the same, then

c, = uoo[aoo - ao] = u[a - a01 (5.56)
Taking the first equation with a, = Q - E

CL = u,[(a - .o) - €1 (5.57)
But equally from Eqn (4.10)
lift per unit span I
c, = =-
f pV2c fpVc
=- PW
4pv2c
217
c, =- (5.58)
VC
Equating Eqn (5.57) and (5.58) and rearranging:
217
-= VI(. - a01 - 4
cam