Vibration Solutions Vibration Solutions
Dr. Brett Marmo
MODELLING AND ANALYSIS OF ACOUSTIC EMISSIONS AND STRUCTURAL VIBRATIONS IN A WIND TURBINE
Presented at the COMSOL Conference 2010 Paris
Introduction
• Environmental noise produced by wind turbines can impinge of residential
communities
• Tonal noise is a particular nuisance and therefore incurs heavy regulatory
Reactec Ltd www.reactec.com
• Tonal noise is a particular nuisance and therefore incurs heavy regulatory
penalties
• Reactec were employed to identify the source of problematic ~600 Hz
tonal noise from a megawatt scale wind turbine
• COMSOL Multiphysics was used to identify structural amplification sources
and to design a cost-effective solution
Mechanical sources of vibration and noise in a wind
turbine
• The turbine manufacturer
identified a tonal
frequency ~ 600 Hz
• This coincides with the
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• This coincides with the
gear meshing frequency
in the gear box
Identifying tonal component30
dBA
15
dBA
WIND
DIRECTION
10 Hz
160 Hz
630 Hz
6.3 kHz
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30
dBA
15
dBA
Key Frequency Emissions
0
5
10
15
6.3
Hz
10
Hz
16
Hz
25
Hz
40
Hz
63
Hz
100
Hz
160
Hz
250
Hz
400
Hz
630
Hz
1.0
k
1.6
k
2.5
k
4.0
k
6.3
k
10.0
k
16.0
k
Av
era
ge
d S
PL
Dif
f.
(dB
A)
Vibration survey
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Yaw test to excite resonances – Gear Box
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Yaw test to excite resonances – Tower Skin
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Turbine active test
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Gearbox 602 Hz modal shape
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Skin frequencies
• The tower of this particular
turbine is made up of two
sections of tubular steel of
varying thickness
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• COMSOL Multiphysics was
used to identify hot spots
where ~600 Hz vibration are
amplified
Vibration – noise pathway
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Acoustic-structural interaction model
• Combines three acoustic time-
harmonic models with a
frequency response model
using shell elements:
• Air in nacelle
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• Air in nacelle
• Air in tower
• Air external
• Excite with a vibration source
in the tower over a range of
frequencies from 5 to 3000 Hz
Acoustic-structural interaction model
• Results of native state
model:
• Sound pressure level as
measured 20 m from the
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measured 20 m from the
base of the tower
Acoustic-structural interaction model
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Conclusion
• COMSOL Multiphysics was used to identify the
modal shapes of structural resonances that amplify
~600 Hz tonal noise
• The identification of modal shapes help identify the
Reactec Ltd www.reactec.com
• The identification of modal shapes help identify the
vibration pathway from gearbox to external air-
borne noise
• Acoustic-structural interaction models were used to
target acoustic hot spots and develop a cost-
effective solution