Sundheds- og Forebyggelsesudvalget 2013-14
SUU Alm.del Bilag 268
Offentligt
1332986_0001.png
Simplified upwind propagation model for
wind turbines
Model description by Birger Plovsing and Jørgen Jakobsen (based on manuscript to be
submitted to Noise Control Engineering Journal)
Input parameters
h
S
: source height (m)
d:
horizontal propagation distance (m)
u
10
: wind speed component 10 m above ground in the direction of propagation (m/s), negative
values in upwind
Fixed model parameters (cannot be changed)
h
R
= 1.5 m: receiver height
z
0
= 0.05 m: roughness length
t
0
= 10° C: air temperature
c(t
0
)
= 337,4 m/s: the sound speed at temperature
t
0
Calculation of
model parameter d’
Wind speed
u
(m/s) as a function of height
z
(m):
z
10
u
z
�½
u
10
ln
 
ln
 
z
z
0
0
Average sound speed gradient
Δ
c/
Δz
(s
-1
):
c u
h
S
u
h
R
�½
z
h
S
h
R
Effective sound speed
c
0
(m/s) at the ground (z = 0) in linear sound speed profile approximation:
c
c
0
c
t
0
u
10
10
z
1
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1332986_0002.png
Relative sound speed gradient
a
(m
-1
):
c
c
0
a
�½
z
Distance to shadow zone d
SZ
(m):
d
SZ
2
h
S
2
h
R
a
a
Horizontal propagation distance relative to shadow zone distance
d’
(dimensionless):
d
 �½
d
d
SZ
Method for determining the A-weighted upwind ground effect
ΔL
u
in excess
of the A-weighted downwind ground effect
ΔL
g
given in
Vindmøllebekendtgørelsen :
The excess A-weighted upwind ground effect
Δ
L
u
in dB is calculated by:
15
if h
S
15
h
S
�½ 
h
S
if
15
h
S
70
70
if h
70
S
h
 
15
k
1
�½
S
0.55
220
h
 
15
k
2
�½
S
2 .1
50
0
if d
 
k
1
d
 
k
1
if k
1
d
 
k
2
L
u
�½ 
15
k
2
k
1

15
if d
 
k
2
Method for determining the upwind low frequency ground effect
ΔL
uLF
in
excess of the one-third octave band downwind ground effect
ΔL
gLF
given in
Vindmøllebekendtgørelsen :
For one-third octave band frequencies below 31.5 Hz
Δ
L
uLF
is equal to 0 dB.
2
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1332986_0003.png
In the frequency range 31.5 Hz to 160 Hz
Δ
L
uLF
in dB is calculated by the following equation where
Δ
L
max
,
k
1
and
k
2
are defined in the table below:
L
uLF
0
if d
 
k
1
d
 
k
1
�½ 
L
max
if k
1
d
 
k
2
k
2
k
1

L
max
if d
 
k
2
Δ
L
max
-3
-6
-10
-14
-15
-15
-15
-15
k
1
3
2.3
2
1.7
1.6
1.5
1.45
1.35
k
2
5
5
5.2
5
4.3
3.6
3.2
3.05
Frequency (Hz)
31.5
40
50
63
80
100
125
160
3