Environmental Engineering Reference
In-Depth Information
Effective slenderness
l
for cylinders with segment length L and outside diameter b to
DIN 1055-4 [12] Table 16:
l ¼
Min
:
ð
0
:
7
L
=
b
;
70
Þ
for L
50 m
l ¼
Min
:
ð
L
=
b
;
70
Þ
for L
15 m
Intermediate values may be obtained by linear interpolation.
Reference area of segment “j” considered (to DIN 1055-4 [12] 12.7.1. (5)):
A
j
¼
L
j
b
j
Calculation of aerodynamic force coefficient
([12] 12.7.1)
Example:
prestressed concrete wind turbine structure, hub height 130m (see
Section 5.2)
Symbol
Reference to
DIN 1055-4 [12]
Value
Height of tower (segment)
¼
reference
height
h
¼
z
e
[m]
12.7.1 (6)
129.674
Width of tower (segment)
b [m]
5.60
Reference wind speed
v
ref
[m/s]
WZ 2
25.0
Reference dynamic pressure
q
ref
[kPa]
WZ 2
0.39
Factor
c
Table B.2
2.10
Exponent
d
Table B.2
0.24
Peak dynamic pressure
q
B
(z
e
)
[kPa]
Table B.2
1.52
¼
40
q
B
0.5
Equivalent wind speed
v (z
e
) [m/s]
49.27
[m
2
/s]
Kinematic viscosity
n
1.5E-05
Reynolds number
Re
Eq. (31)
1.8E
þ
07
Equivalent roughness
k [mm]
Table 11
10
Relative roughness
k/b
0.00179
Basic force coefficient
c
f,0
Figure 19
0.991
Slenderness
l
Table 16
16.21
c
l
Reduction factor
Figure 26
0.752
Force coefficient for tower shaft
c
f
Eq. (30)
0.75
