Environmental Engineering Reference
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Figure 7: Pressure coeffi cient around an airfoil.
Figure 8 : Lift and drag around an airfoil; v is a sample infl ow velocity and is not
to be confused with a relative velocity.
defi ned as the lift-to-drag-ratio L / D . Usually this number is around 100. In total
Figs. 10 and 11 are obtained. Compared to Fig. 3 the quantitative infl uence of drag
and fi nite bladenumber on c P are presented. In addition Fig. 6 shows the improve-
ment of state-of-the art commercial wind turbines of one manufacturer over a span
of 20 years. Clearly one can see that high-performance airfoils have to be used to
reach for a
ma c in the order of 0.52. It is clear that B = 1 is very special, and one
might assume that no such turbines were manufactured. This in fact was not the
case. In the late 1980s the German company MBB manufactured the so-called
Monopteros (see Fig. 9), a single-blade turbine. To demonstrate the big differences
data from Rohrbach et al. [46] is included.
p
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