Vibration Solutions - comsol.it fileVibration – noise pathway Reactec Ltd . Acoustic-structural...

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

http://www.comsol.com/conf_cd_2011_eu

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


• 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


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


Yaw test to excite resonances – Gear Box


Yaw test to excite resonances – Tower Skin


Turbine active test


Gearbox 602 Hz modal shape


Skin frequencies

• The tower of this particular

turbine is made up of two

sections of tubular steel of

varying thickness


• COMSOL Multiphysics was

used to identify hot spots

where ~600 Hz vibration are

amplified

Vibration – noise pathway


Acoustic-structural interaction model

• Combines three acoustic time-

harmonic models with a

frequency response model

using shell elements:

• Air in nacelle


• 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


• Results of native state

model:

• Sound pressure level as

measured 20 m from the


measured 20 m from the

base of the tower

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


• 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

Vibration Solutions - comsol.it fileVibration – noise pathway Reactec Ltd . Acoustic-structural...

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