simulation of noise treatments in aircraft
TRANSCRIPT
5th European HyperWorks Technology Conference 111107
Peter Davidsson
Simulation of noise treatments in aircraft
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
Competences • Vibro-Acoustic FEM
• Propeller Noise
• ECS Noise
• Noise & Vibration Measurements and Analysis
• Active Noise Control
• Tuned Vibration Absorbers
• Acoustic Liners
Creo Dynamics – Strategi
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
6
Aerospace acoustics A 400M Saab 2000 and Gripen
Controller
Cabin acoustics
First modes of a cabin structure
Noise box – trim panels
System design Pre study
Measurement
Correlation
Noise box – trim panels
Panel
Porous material – structural domain
Porous material – fluid domain
Acoustic cavity
Biot’s formulation for porous material
Generic Car; Rear Side Window Buffeting
Microphone location
Buffeting 110 Db, 22Hz
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Aerospace acoustics - A400M
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
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
Simulation of noise treatments in aircraft
Monitor microphones
Control microphones Actuators
External pressure field
act
act
monextmon TF Fpp ][
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 ][
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
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
– …
Simulation procedure
• Finite element model generation
• External pressure field
• Preloading
• Primary field
• Dynamic condensation
• Optimization – Actuator properties
– Actuator and control sensor location
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
Actuator dofs and monitor dofs
Monitor
TVA, shaker
Helmholtz, loudspeaker
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
Preloading due to cabin pressure
Primary respons, structure
2.BPF 1.BPF
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
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?
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
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
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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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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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
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
Reduction in monitor nodes 1.BPF
PassiveTVA’s
ANC, Shakers
Primary field
Reduction in monitor nodes 2.BPF
PassiveTVA’s
ANC, Shakers
Primary field
System size
PassiveTVA’s
ANC Shakers and microphones
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
Thank you
• Contacts:
– Peter Davidsson
– Gustav Kristiansson (VD)