Simulation of noise treatments in aircraft
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Transcript of Simulation of noise treatments in aircraft
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5th European HyperWorks Technology Conference 111107
Peter Davidsson
Simulation of noise treatments in aircraft
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Creo Dynamics AB
• Started in January 2010
• Office in Linköping and Lund
• Key persons with background from A2 Acoustics and Saab Aerospace
• 13 employees
• Extensive experience in Aerospace Acoustics
• SME
• Link between the research community and industry
• Multidisciplinary acoustic challenges: acoustics, structural dynamics, fluid mechanics and composites
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Competences • Vibro-Acoustic FEM
• Propeller Noise
• ECS Noise
• Noise & Vibration Measurements and Analysis
• Active Noise Control
• Tuned Vibration Absorbers
• Acoustic Liners
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Creo Dynamics – Strategi
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Creo Dynamics – Kompetenser
Akustik
Creo Dynamics utvecklar både aktiva och passiva lösningar för att förbättra ljud och vibrationsegenskaper hos produkter
Aero-/Termodynamik
Experter inom CFD och termodynamiska beräkningar
Strukturdynamik
Experter inom såväl struktur- dynamik som vibro-akustik och akustisk utmattning
Kompositer
Design och analys av produkter i kompositmaterial
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6
Aerospace acoustics A 400M Saab 2000 and Gripen
Controller
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Cabin acoustics
First modes of a cabin structure
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Noise box – trim panels
System design Pre study
Measurement
Correlation
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Noise box – trim panels
Panel
Porous material – structural domain
Porous material – fluid domain
Acoustic cavity
Biot’s formulation for porous material
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Generic Car; Rear Side Window Buffeting
Microphone location
Buffeting 110 Db, 22Hz
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A2Z-PS-08-028 2011-11-14
11
Aerospace acoustics - A400M
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Integrated optimization
• Increasing interest in turboprop and open rotor powered aircraft
• Active Noise and Control Systems development starts when aircraft structure and cabin interior design is fixed
• Far from optimum due to severe constraints, e.g. for actuator locations and attachments
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Integrated optimization
• Identified need for joined optimization of both structure, cabin interior and noise control system
• Hyperworks products very suitable for integrated optimization
• Radioss
• Hyperstudy
• Optistruct
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Simulation of noise treatments in aircraft
Monitor microphones
Control microphones Actuators
External pressure field
act
act
monextmon TF Fpp ][
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Simulation of noise treatments in aircraft
• Aim:
– Minimize noise level in monitor microphones
– Limited to low frequency tonal noise
Primary field Total field
act
act
monextmon TF Fpp ][
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Simulation of noise treatments in aircraft
• Aim:
– Minimize noise level in monitor microphones
• Means:
– Passive noise control system
– Active noise control system
• Design
– Finite element simulations for evaluation of system properties
– The actuator and sensor location determines the system performance
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Simulation of noise treatments in aircraft
• Simulations can be used for studying:
– Potential in different treatments
– Size of the system
– Mounting conditions
– Sensitivity in modifications in the structure and acoustic cavity
– Sensitivity to changes of external pressure field
– …
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Simulation procedure
• Finite element model generation
• External pressure field
• Preloading
• Primary field
• Dynamic condensation
• Optimization – Actuator properties
– Actuator and control sensor location
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Finite element model generation
p
d
d
0
0
F
0
F
F
FRFFRFFRF
FRFFRFFRF
FRFFRFFRF
s
d
d
d
ext
s
ext
d
pppspd
spsssd
dpdsdd
FdKM 2
FFRFFDd 1
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Actuator dofs and monitor dofs
Monitor
TVA, shaker
Helmholtz, loudspeaker
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External pressure field
• Shortcut (no CFD)
• BEM including flow
• Mapped to FEM
0
F
F
FRFFRFFRF
FRFFRFFRF
FRFFRFFRF
p
d
dext
s
ext
d
pppspd
spsssd
dpdsdd
ext
ext
s
ext
d
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Preloading due to cabin pressure
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Primary respons, structure
2.BPF 1.BPF
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Primary respons, acoustic cavity
d
dd
ext
d
d
pppspd
spsssd
dpdsdd
ext
ext
s
ext
d
s
d
FFRFd
0
0
F
FRFFRFFRF
FRFFRFFRF
FRFFRFFRF
p
d
d
p
d
d
How do we get the actuator force?
The equation system can now be written:
2.BPF 1.BPF
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Simulation of noise treatments in aircraft
• Available treatments
Actuator Sensor Actuator force
Passive Dynamic vibration absorbers
F from local displacement
Helmholtz resonator
Q from local acoustic pressure
Active Shaker/ Piezo actuator
Accelerometer F from ANC system
Microphone
Loudspeaker, Active panel
Microphone Q from ANC system
Still, how do we get the actuator force?
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Passive, Tuned vibration absorbers
• Change the dynamic stiffness, do not absorb vibration
m
)1(~
iLFkk
)(sx
)(dx
m
dF
)(2 smountd xmF
mmount
sds
n
nd xhxkF
1
22
2~
dsd xmxxk 2~
sdd xxkF ~
Force in the spring: Equiv. dyn mass Force can be written
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Passive, Tuned vibration absorbers
• Change the dynamic stiffness, do not absorb vibration
m
)1(~
iLFkk
)(sx
)(dx
m
dF
)(2 smountd xmF
mmount
d
ddd
ext
dd FFRFdd
dddddddd
d
d h dIdHF
ext
ddddddd
d
d dHFRFIHF1
For the actuator dofs: The TVA force Force can be written
A system of size equal to the number of included TVA’s needs to be solved for each configuration
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Active Noise Control system Actuator forces
IFFQeeTT
– Acoustic pressure in the control microphones
– The primary response in the control microphones from the external
pressure field
– The actuator forces
– The frequency response functions between the force actuators and
control microphones
– Determine the control effort (leak factor in the LMS-algorithm)
- Determine the influence of each microphone on the cost function
Object to minimize the function
e
TT
act QpTFITFQTFF ][][][1
act
act
ctrle FTFpe ][
ep
e
actF
TF
Q
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A2Z-PS-08-028 2011-11-14
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Actuator forces
• The passive system reduce the local vibration/pressure level, based on the local properties.
• The ANC system determines the driver signals for the actuators, i.e. the actuator forces, based on the SPL in the control sensors.
– In the cabin, the control microphones are placed at the trim panels.
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A2Z-PS-08-028 2011-11-14
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Analysis procedure
• The aim is to find the optimal configuration of actuators and control microphones in order to minimize the noise inside the cabin.
• The primary response and FRF’s are derived once for each frequency line
• The best configuration is then searched for in an optimization procedure
– Finding the “optimal” force
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Optimization procedures
• Different procedures may be used to optimize a noise controlling installation: – Maximum amplitude. The tuned vibration absorbers are
placed in the positions where the maximum displacement occurs in the baseline analysis.
– Sequential maximum amplitude. The first tuned vibration absorber is placed where the maximum vibration amplitude occurs in the baseline analysis. The system is then re-analyzed and the next damper is placed where the vibration now has its maximum. This is repeated until all DVA-positions are determined.
– Simulated annealing • Both active and passive systems
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Optimization procedure (Simulated annealing)
• Present configuration
• All available locations
• Monte Carlo simulations
– The new configurations are derived by randomly choosing a number of devices (actuators and microphones) from the present configuration and randomly choosing a number of devices from all possible positions.
– Annealing factor
– Only solving a system with size equal to the number of actuators
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Reduction in monitor nodes 1.BPF
PassiveTVA’s
ANC, Shakers
Primary field
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Reduction in monitor nodes 2.BPF
PassiveTVA’s
ANC, Shakers
Primary field
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System size
PassiveTVA’s
ANC Shakers and microphones
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Results example
• Potential in noise reduction Actuator Sensor Potential
1.BPF 2.BPF 3.BPF
Passive Dynamic vibration absorbers
8-12 4-7 0
Helmholtz resonator
8-12 4-7 0
Active Shaker Accel. 10-15 5-8 1-3
Microphone 15-25 8-12 2-4
Loudspeaker Microphone 15-25 8-12 3-6
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Thank you
• Contacts:
– Peter Davidsson
– Gustav Kristiansson (VD)