less noise, more safety! - ku leuven · noise in europe 2014 –eea report “at least 1 million...

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



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



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



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


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


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


How to reduce noise?

Limit the sources of sound

waves

Reduce the propagation of

sound waves

Source Listener

Concepts


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)


Less Noise

Aircraft liners


Sound Quality

Perforated panels for room acoustics


More safety

Perforated plates and resonators in

combustion engines

FLAME

FLOW ACOUSTIC

Combustion

instabilities


More safety

Perforated plates and resonators in

combustion engines

FLAME

FLOW ACOUSTIC

Combustion

instabilities

Rocket thrust chamber

Burner

SILENCERS


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)


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 %)


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


Vibration /

Structural

behavior

Fully coupled

vibro-acoustic

FEM model

19

Develop numerical methods

• To perform parametric studies optimization


• 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


impedance models

p1

p2

U1 = U21

2

nU

pZ

.

1

21

U

ppZt


21

Improved modelling

p1

p2

U1 = U2

1

21

U

ppZt

1

2

nU

pZ

.

Automotive muffler



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


Is there no other alternative?


Hybrid methods: Propagation

Flow Acoustics

Source: Wikipedia

Large differences (especially for M<<1)

<< Length scales <<

<< Time scales <<

>> Energy >>

<< Propagation <<


Large differences (especially for M<<1)

<< Length scales <<

<< Time scales <<

>> Energy >>

<< Propagation <<

24


Flow Acoustics

Incompressible Compressible



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


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:


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


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


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


31

Finite Element Method (FEM) Solver


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


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


34



Investigated case

𝒕 = 𝟒 𝒎𝒎

𝒅 = 𝟐𝟎 𝒎𝒎

𝑯 = 𝟒 𝒄𝒎

𝑳 = 𝟓𝟎 𝒄𝒎

35



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

′


37

Plate orifice under bias flow condition

Vorticity field at frequency f = 1000 Hz

Quasi-laminar LNS -

ABL resolved


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”


THANK YOU FOR

YOUR ATTENTION.

Questions?

Contact:

Jonathan Tournadre

PhD candidate at KU Leuven, PMA Mechanical Dpt.

Noise & Vibration Research Group

[email protected]

22nd February 2017

less noise, more safety! - ku leuven · noise in europe 2014 –eea report “at least 1 million...

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