Aerofoils: Lift, Drag, and Circulation - Small Wind Turbines: Analysis, Design, and Application - page 66

Table 4.3 Source of data for Figs. 4.6 and 4.7

Symbol Source Aerofoil Re

1.6 9 10 5 + Fage and Johansen [ 12 ] Flat plate

10 5 9 Kogaki et al. [ 5 ] MEL 081

10 5 * Bruining [ 15 ] Cambered flat plate

6 9 10 4

r

Bruining [ 15 ] Cambered flat plate

5.1 9 10 4 O Zhou et al. [ 11 ] NACA 0012

1.05 9 10 4

Zhou et al. [ 11 ] NACA 0012

5.3 9 10 3 h Zhou et al. [ 11 ] NACA 0012

Fig. 4.6 a High-angle lift
coefficient for Reynolds
numbers below 2 9 10 5 .
b High-angle drag coefficient
for Reynolds numbers below
2 9 10 5 . Data sources listed
in Table 4.3

(a)

1.4

1.2

1

C l = 2sin cos α

α

0.8

0.6

0.4

0.2

0

20 30 40 50 60 70 80 90

angle of attack ( ° )

(b)

2

1.5

C d = 2sin 2

1

α

0.5

20 30 40 50 60 70 80 90

angle of attack ( ° )

4.5 The Circulation

Section 3.4 considered the two-dimensional analogue of the axisymmetric blade
elements at radius r. This analogue is sketched in Fig. 4.8 , where only four of the
infinite cascade of aerofoils (up and down the page) is shown. In terms of the blade
element chord, c, the non-dimensional spacing between the elements is just the
inverse of the solidity, r, defined by Eq. 3.14 . Now assume for simplicity that the