Civil Engineering Reference
In-Depth Information
FIGURE 4-10
Weibull distributions of hours/year with three different shape parameters k = 1.5, 2, and 3.
Since most wind sites would have the scale parameter ranging from 10 to
20 miles per hour (about 5 to 10 m/s), and the shape parameter ranging
from 1.5 to 2.5 (rarely 3.0), our discussion in the following sections will center
around those ranges of c and k.
Figure 4-10
displays the number of hours on the vertical axis versus the
wind speed on the horizontal axis with distributions of different scale param-
eters c = 10, 15, and 20 mph and shape parameters k = 1.5, 2, and 3. The
values of h in all three sets of curves are the number of hours in a year in
the speed interval v +
v.
Figure 4-11
depicts the same plots
in the three-dimensional h-v-k space. It shows the effect of k in shifting the
shape from the bell shape in the front right hand side (k = 3) to the Rayleigh
and flatter shapes as the value of k decreases from 3.0 to 1.5. It is also
observed from these plots that as c increases, the distribution shifts to the
higher speed values.
∆
v divided by
∆
