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Less noise, more safety!Numerical methods for improved silencers
designs
22nd February 2017
Jonathan Tournadre
Mechanical Engineering, PMA,
Noise & Vibration Research Group
Outline of the talk
2
1. Research activities on noise control
2. Passive silencers: applications and challenges
3. Hybrid acoustic methodology applied to the linear
regime of silencers and perforates
• Physics of sound propagation in
non-uniform flow
• Example: orifice with bias flow
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 3
Aero-acoustics research group
Part of the Noise & Vibration research group
Aero-acoustics
Vibro-acoustics
Structural Reliability, Monitoring &
Uncertainty
Multi-body Dynamics
Smart System
Dynamics
Visit our website: https://www.mech.kuleuven.be/en/research/mod
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 4
Aero-acoustics research group
Head of the group,
Full Professor
Industrial Research
Manager Assistant
Professor
Vyacheslav
Korchagin
Antonio
Ammirati
Bert PluymersWim Desmet Wim De Roeck
Maria Muriel
Gracia
Hervé
Denayer
Jonathan
Tournadre
Ali Hussain
Kadar
PhD researchers
The team
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 5
Aero-acoustics research group
Research objectives
Develop numerical and experimental methods to
Better understand the physics of sound-
flow interaction
Gain better acoustic characterization of complex systems
Measure and predict acoustic sources
Efficiently incorporate acoustics in the design of
industrial systems
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 6
Aero-acoustics research group
Research topics
Test rig for measurement in
confined flows
Numerical methods for acoustic wave propagation
through non-homogeneous flow regions
New experimental source
identification strategy
Stochastic noise reconstruction methods
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 7
Noise Pollution
Burden of disease from environmental noise – World Health Organization 2011
Noise in Europe 2014 – EEA Report
“at least 1 million healthy life years are lost every year in western Europe due to
health effects arising from noise exposure to road traffic alone”’
Noise is the second-worst environmental cause of
ill health in Europe
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 8
Noise Pollution
Burden of disease from environmental noise – World Health Organization 2011
Noise in Europe 2014 – EEA Report
Tinnitus
Annoyance
Sleep Disturbance
Cognitive
Impairment
Cardiovascular
Disease
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 9
How to reduce noise?
Limit the sources of sound
waves
Reduce the propagation of
sound waves
Source Listener
Concepts
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 10
How to reduce noise?
Barriers
Poroelastic materials
Viscous layers
Actives or structural
actuators
Technical solutions
P
A
S
S
I
V
E
S
O
L
U
T
I
O
N
S
(e.g. Resonators, Perforated Plates, Liners)
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 11
Less Noise
Aircraft liners
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 12
Sound Quality
Perforated panels for room acoustics
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 13
More safety
Perforated plates and resonators in
combustion engines
FLAME
FLOW ACOUSTIC
Combustion
instabilities
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 14
More safety
Perforated plates and resonators in
combustion engines
FLAME
FLOW ACOUSTIC
Combustion
instabilities
Rocket thrust chamber
Burner
SILENCERS
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 15
Passive silencers
What are we looking at?Passive Noise Control Components
Helmholtz
resonators
Quarter-wave
resonatorsPlates / Pipes
with orifices
Liners Micro-Perforated
Plates
Damp acoustic waves
(with orifices)
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 16
Passive silencers
How does it work?
m
k
Air in orifice
Backing cavity
Absorption coefficient of a MPP
(with 69 holes, d = 0,5 mm, σ = 0,2 %)
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 17
Passive silencers – design parameters
Visco-thermal effects:
Non-isentropic
conditions
Flow effects: convection and shear
Flow Flow
grazing flow Bias flow
Excitation amplitude: Linear and
nonlinear regimes
Vibration /
Structural
behavior
Turbulent mixing
Different applications,
many challenges
18
Example: Impact of vibrations
Absorption coefficient of a MPP
(with 69 holes, d = 0,5 mm, σ = 0,2 %)
structural shell
elements
acoustic transfer
admittance model
3-D acoustic
elements
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
Vibration /
Structural
behavior
Fully coupled
vibro-acoustic
FEM model
19
Develop numerical methods
• To perform parametric studies optimization
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
• To improve existing acoustic models to use in larger
systems
Reliable and accurate acoustic
impedance models
• To develop new design of acoustics dampers
20
Improved modelling
Reliable and accurate acoustic
impedance models
p1
p2
U1 = U21
2
nU
pZ
.
1
21
U
ppZt
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
21
Improved modelling
p1
p2
U1 = U2
1
21
U
ppZt
1
2
nU
pZ
.
Automotive muffler
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
Reliable and accurate acoustic
impedance models
22
Improved modelling
• Need for models to use in larger systems
o Scale-resolving simulations such as Direct Numerical Simulation (DNS)
o Semi-empirical models
Computationally costly
Limited validity range
Hybrid numerical aeroacoustics
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
Is there no other alternative?
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 23
Hybrid methods: Propagation
Flow Acoustics
Source: Wikipedia
Large differences (especially for M<<1)
<< Length scales <<
<< Time scales <<
>> Energy >>
<< Propagation <<
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
Large differences (especially for M<<1)
<< Length scales <<
<< Time scales <<
>> Energy >>
<< Propagation <<
24
Hybrid methods: Propagation
Flow Acoustics
Incompressible Compressible
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 25
Hybrid methods: Propagation
Variable perturbations << Variable mean values
𝑝′( 𝑥, 𝑡) 𝑝0( 𝑥, 𝑡)
o Limited to low Sound Pressure Level (<130 dB)
Linear regime
Weak coupling: one way interaction
Flow Acoustics
Flow Acoustics
A
s
s
u
m
p
t
i
o
n
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 26
Propagation operator
In a quiescent, homogeneous medium:
Spherical waves
coming from a
point source (3-D)
A pulse traveling through a string
with fixed endpoints (1-D)
𝜕2𝑢
𝜕𝑡2 = 𝑐2 𝜕2𝑢
𝜕𝑥2
𝜕2𝑢
𝜕𝑡2 = 𝑐2𝛻2𝑢
Linearized Navier-Stokes Equations (LNSE)
Wave equation
In presence of flow, for our silencers:
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 27
CAA Tools Overview
Linearized Navier Stokes
Equations (LNSE)
Linearized Euler Equations
(LEE)Neglect viscosity
and heat transfer
Hybrid Approach (Linearized)
Neglect nonlinear effects
Acoustic Perturbation
Equations (APE)
Neglect
hydrodynamic
modes
Linearized Potential Theory
(scalar equation) Assume
irrotational
mean flow
Helmholtz EquationNo mean flow
Two-stage calculations: predict the base flow and aero-acoustic sources first, then
calculate propagation of small perturbations.
DIRECT Approach
Navier-Stokes Equations
• DNS
• LES (w/ subgrid scales)
URANSUse of turbulence
modeling
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
Y-velocity field for base flow
CF
D
• Computation of base flow
• Mapping of this base
flow
28
Hybrid methodology applied to perforatesL
NS
E s
olv
er
Po
st-
pro
cessin
g • Impedance value estimation
In-situ technique / Multi-port characterization / Eduction methods
Propagation of the acoustic
wave with LNSE operator
• Acoustic energy dissipation and production
Num
erical C
AA
hybrid m
eth
odolo
gy
RANS simulations
Jonathan Tournadre Arenberg Youngster Seminar – February 2017 29
LNS set of equations
Flow decomposition:𝑝 = 𝑝0 + 𝑝′
Total flow variable = Base flow + Perturbations
Set of equations:
with
(Continuity)
(Momentum)
(Energy)
30
LNS set of equations
Conservative form of LNSE after linearization:
Time variation
Flux matrices
Non-uniform mean flow effects
Viscous and thermal
effects
Assumptions:o Variable perturbations << Variable mean values,
o Perfect gas
with
Source terms
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
31
Finite Element Method (FEM) Solver
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
Approximation of
the field variables
…
Φ00
Φ01Φ10
Φ11Φ20 Φ02
Φ30
Spatial
Discretization
Runge Kutta Discontinuous
Galerkin (RKDG) code
TIME DOMAIN
32
Finite Element Method (FEM) Solver
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
Approximation of
the field variables
Spatial
Discretization
Runge Kutta discontinuous
Galerkin (RKDG) LNSE code
TIME DOMAIN
Optimized Runge-Kutta time
integration scheme:
Weak formulation
of the problem
T
𝜕T
Time
Discretization
8 stage 4th-order RK scheme
33
Examples of applications cases
Visco-thermal effects in a
small closed duct
600 Hz
Entropy interior source in a nozzle
Slit resonator with
grazing cold flow
[𝒌𝒈
𝒎𝟑 ]
Orifice with turbulent bias flow
100 200 300 400 500 600 70070
80
90
100
110
120
130
140
150
Frequency f [Hz]
Re
sis
tan
ce [
rayl]
LNS with h = 0.30 mm,
s = 30 deg
Experimental results
LNS with h = 0.36 mm, s = 29.9 deg
Micro-Perforated
Plate impedance
Acoustic wave propagation
from monopole in flow
boundary layer over a plate
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
34
Orifice with turbulent bias flow
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
Investigated case
𝒕 = 𝟒 𝒎𝒎
𝒅 = 𝟐𝟎 𝒎𝒎
𝑯 = 𝟒 𝒄𝒎
𝑳 = 𝟓𝟎 𝒄𝒎
35
Orifice with turbulent bias flow
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
Investigated case
𝑴 ≈ 𝟎. 𝟎𝟒
𝑺𝒕 ∈ 𝟎. 𝟎𝟐 − 𝟎. 𝟓𝟐
𝑹𝒆 ≈ 𝟒. 𝟏𝟎𝟒
36
Plate orifice under bias flow condition
Quasi-laminar LNS results for the real part of the density ρ’ (left) and velocity component 𝝆𝟎𝒖′𝒙 (right)
perturbations at frequencies: f = 1000 Hz (top), f = 3000 Hz (center), f = 5000 Hz (bottom).
[𝒌𝒈
𝒎𝟐. 𝒔][
𝒌𝒈
𝒎𝟑]𝜌′ 𝜌𝑢𝑥
′
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
37
Plate orifice under bias flow condition
Vorticity field at frequency f = 1000 Hz
Quasi-laminar LNS -
ABL resolved
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
38
Take-away messages
Design parameters
Understanding of the
physical phenomena
and their impact
Improve design of
silencers
Gaining accurate
impedance models
Efficient numerical
CAA methods
“From challenges to enhanced modeling capability”
Jonathan Tournadre Arenberg Youngster Seminar – February 2017
THANK YOU FOR
YOUR ATTENTION.
Questions?
Contact:
Jonathan Tournadre
PhD candidate at KU Leuven, PMA Mechanical Dpt.
Noise & Vibration Research Group
jonathan.tournadre@kuleuven.be
22nd February 2017
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