Wind Turbine Aerodynamics Part A: Basic Principles - Wind Turbine Technology: Fundamental Concepts of Wind Turbine Engineering - page 296

Table 5-3.
Blade Chord and Twist Distribution for an Optimum Two-Bladed HAWT
(Lift coefficient = 0.8 and tip-speed ratio = 6)

Velocity
ratio
x

Radial
position
r / R

Chord
ratio
c / R

Twist
angle
b (deg)

0.75 0.125 0.363 28.1

1.50 0.250 0.298 15.2

3.00 0.500 0.180 5.0

4.50 0.750 0.125 1.0

6.00 1.000 0.095 -1.0

Flow States

In the previous analysis, it was tacitly assumed that the wind turbine is operating as a
power-extraction device that produces a downwind force and retards the free-stream wind
speed. This requires that the axial induction factor be between zero and unity. Figure 5-11(a)
shows flow patterns or flow states and thrust force vectors T associated with a wide range of

Figure 5-11. Relationship between the axial induction, flow state, and thrust of a
rotor. [Lock et al. 1926, Wilson et al. 1976]