Environmental Engineering Reference
In-Depth Information
Poul la Cour did not develop a new formula, but he developed
a diagram to determine the best design of a sail based on very
careful and precise measurements. It is called the “mussel” diagram,
because the shape of it reminds about the mussel, which is very
common along the Danish coastlines. With this diagram available
a millwright should be able to complete the practical work to an
optimum of efficiency. With the wind flow of 1 m/s determined
from the small wind tunnel, he measured the influence successively
on a plane, a curved and a bent profile with dimensions 10 cm ×
10 cm.
Figure 4.13
Graphical representation of the measurements, the “mussel”
diagram.
The origin of the diagram is the rotational centre of the sail.
The numbers on the horizontal axis are the bevel angles of the
sail to the rotation plane. The numbers on the vertical axis are the
velocity factors for that particular point of the sail compared to
the velocity of the incoming wind. The diagram gives the impression
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