Environmental Engineering Reference
In-Depth Information
Fig. 2.15 Magnitude of wind direction change for ECD
8
<
V ð z Þ
for
t
<
0
5 V cg ð 1 cos ðp t
=
T ÞÞ
0 t T
V ð z
;
t Þ¼
V ð z Þþ 0
:
for
:
V ð z Þþ V cg
>
for
t
T
where
Þ a
V ðÞ¼ V hub
ð
z
=
z hub
ð NWP
;
see above Þ
and
T ¼ 10 s
gust rise time
Extreme coherent gust with wind direction change (ECD)
In this situation we assume, as with the ECG, that the rise in the wind speed takes place
simultaneously with a change in direction (
u cg ), which is described as follows (see
Figure 2.15):
(
180
for V hub <
4m
=
s
u cg V hub
ð
Þ¼
720 =
V hub m
½
=
s
for 4 m
=
s V hub V ref
The resulting simultaneous change in direction is as follows (see Figure 2.16):
8
<
0
for
t
<
0
t Þ¼
0
:
5 u cg ð 1 cos ðp t
=
T ÞÞ
for
0 t T
:
u cg
for
t
>
T
Fig. 2.16 Simultaneous chronological progression of wind direction change for ECD
Search WWH ::




Custom Search