Penn State 2012 Center for Acoustics and Vibration Workshop · Title: Boeing Weston Penn State CAV...

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Penn State – 2012 Center for Acoustics and Vibration Workshop

Aircraft Cabin Acoustic Modeling 2012 Penn State Center for Acoustics and

Vibration Workshop

Adam Weston Senior Structural-Acoustics Specialist Interior Noise Technology May 2012


Penn State - 2012 CAV Workshop | Aircraft Cabin Acoustic Modeling

Adam Weston, May 2012 2

Overview

Aerospace Modeling Approach

• Verify – Simulate - Fly

Cabin Noise Sources

Cabin Treatments

Tools

• SEA

• FEM/BEM

• Database Methods

FEM/BEM Applications

Automation Role

Summary and Opportunities




Aerospace Modeling Approach

Acoustic Simulation Role

Simulate Optimize

Noise/Weight/Cost

Fly Verify Processes

Structural

Components

Field point meshField point mesh

Acoustic

Response

Sources Air

Fuselage

skin

Insulation 1

Insulation 2

Trim

SeptumAir

Fuselage

skin

Insulation 1

Insulation 2

Trim

Septum

Treatment

Verify State-of-the-Art

Δflight= Lflight - Lmodel Lflight Lmodel




Cabin Noise Sources

Aircraft Walkaround

Interior • Environmental System

• Equipment “vibration” noise

• Galley and Lavatories

Exhaust Shock-cells

Engine Noise

Fan Inlet

Vibration




Cabin Noise Sources

Flight Variation

dB

A

Takeoff

Climb Cruise Descent

Thrust

Reverse

Taxi Taxi

Time

Jet Noise

Buzz-Saw

Turbulent Boundary Layer

Shock Cell

Shock-cell



Thrust Reverser

Jet Noise




Cabin Acoustic Treatments

Aircraft Walkaround

Inlet Lining (buzz-saw)

Nozzle/Chevrons (shock-cell)

Balance/Vibration (EVRN)

Structural Damping Constrained layer

Flow resistance

Particle

Blankets Fiberglass

Bagging materials

Mass septum

Foams

Over blankets

Active Noise/Vibration Control Engines / EVRN

ANC zonal / headsets

Smart Foams

Fluidic Wall paper

Isolation Mounts ECS/Equipment /Tie Rods

Flight control actuators

Engines / APU

Tuned Vibration Absorbers

Acoustic Absorption Seats & surfaces

Floor coverings

Acoustic panels

ECS system Reactive / resistive mufflers

Flow rates / pipe sizes

Diffusers / flow restrictors

Fans & powered equipment

Air return grill

ramp noise

Fluids in Pipes hydraulics

Doors

Hatches

& Latches Trim system trim panels

floors

stow-bins

monuments

APU (ramp noise)

FEM/BEM Focus




Tools

Evolution

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1990 1995 2000 2005 2010 2015

Year

% T

oo

l U

sa

ge

Empirical

FEM

SEA

BEM

Ray Tracing CFD

For Project X, my

preferred tools are?




Tools

Structural Acoustics Design Tools

System response is determined by interaction of all components

SEA • Mid to high frequencies

• Systems Cabin, Sidewall, Equipment Transfer Function,

Large test articles

• Simple source representation

FEM • Low frequencies (Engine Rumble/EVRN)

• Small systems, components, detailed design skin pocket, insulation, damping, isolation,

mufflers

External radiation/diffraction, e.g. ramp

• Complex source representation – TBL, shock cell, buzzsaw

• Hybrid components (damping, mufflers)

Database • Close derivative

• Quick turnaround

• Model verification

Normalized data

dB3

dBdB 210




Building Semi-empirical Source Models

Raw data sets Normalized data

Check

Data / Predictions

Prediction curve

The increase in the

uncertainty over the

measurement uncertainty is

due to limitations of the

scaling rules used to

normalize the basic data.

Scaling rules are required

to apply the data to new

situations.

Measurement Uncertainty

Physics

Engineering

dB1

dBdB 210

dB5

dB3

dB2

dB3

dB2

Sc

ali

ng

Un

ce

rtain

ty




Correlated Sources

FEM/BEM vs. FEM-only

BEM/FEM Analysis

• NASTRAN/Virtual Lab

• Coupled Structural-Acoustic

• Cross-spectra of Pressure

• Acoustic Loading

FEM Analysis

• NASTRAN

• Uncoupled Structural

• Cross-spectra of Force

• No Acoustic Loading

Computational Efficiency

Cross-Spectra Decomposition Partition of Aero-acoustic Loading




Application Example – Turbulent Boundary Layer

Nastran vs. Virtual Lab

1.0E-16

1.0E-15

1.0E-14

1.0E-13

1.0E-12

1.0E-11

100.0 120.0 140.0 160.0 180.0 200.0 220.0 240.0 260.0 280.0 300.0

Frequency (Hz)

Dis

pla

cem

ent

PS

D

Nastran (partition 10 x 10)



sysnoise (vector=200)



NASTRAN

- Subdivide the structure

- Smaller number of partition:

overpredict

Virtual Lab

- Smaller number of vector: underpredict

NASTRAN

Virtual Lab



Adam Weston, May 2012 13 Axial Coordinate

Axial Coordinate (inch)

Wa

terl

ine

Co

ord

ina

te(i

nch

)

1600 1650 1700 1750 1800 1850 1900

100

150

200

250

300

350

SPLTOB

114

113

112

111

110

109

108

107

106

105

104

103

102

101

100

99

98

97

96

95

94

777-200 / Trent800 QTD1 Flight Test Data,Condition 103, Nozzle Pressure Ratios 1.71 / 2.46Third Octave Band Spectrum Level at 1 KHz

dpred05

Axial Position (inch)

Ba

nd

#

1600 1650 1700 1750 1800 1850 1900

20

25

30

35

40

SPLTOB

114

113

112

111

110

109

108

107

106

105

104

103

102

101

100

99

98

97

96

95

94

dpred06

777-200 / Trent800 QTD1 Flight Test Data,Condition 103, Nozzle Pressure Ratios 1.71 / 2.46Third Octave Band Spectrum Level at angular position 75 deg.

Application Example

Shock Cell

Axial Coordinate

Fre

qu

ency

Ban

d

Wat

erli

ne

Co

ord

inat

e

Semi-Empirical Source Models Exterior Fluctuation Pressures

SEA Model

FEM Model




Diffuse and Aero-Acoustic Sources

Generalized Complex Cross-Spectra

Power

Spectra

Spatial

Coherence

Phase

Base Form

Diffuse Random No phase

TBL

Shock Cell

yyxx SS 2

xy

xyie

xyS

kr

krsin)(11 S),(12 rS

wUi phe/1

2

2

1

1

ee),,( 2112 S

),,( 2112 ie

5.02

2

22

1

1 ]))(

())(

[(

LLe

),,( 2112 S

yyxx SS ,

2xy

Power spectra of the pressure field

Coherence of the pressure field

Phase factor

Separation distance between nodes

Separation distances (flow, cross-wise)

Correlation length scales (flow, cross-wise)

Phase velocity

Correlation length w.r.t. engine nozzle

ie

2,1

2,1

phU

r

2,1L

2211 SS

2211 SS




FEM Application Example – Low Frequency

Engine Vibration Related Noise

Sidewall System (Biot Theory)

Structure (Entire Aircraft) Excitation (Rotor Dynamics)

Rotating shafts

Acoustic

(FEM)

Strut




Interior Panel •mass per unit area

•coincidence frequency

•damping loss factor

•Structural isolation

Insulation •flow resistance

•mass per unit area

•Thickness

•No leaks

Fuselage Structure •mass per unit area

•damping loss factor

•coincidence frequency

Cabin Acoustic Treatments Sidewall System Design

SEA entire system modeling

FEM/BEM focus is components

• Damping on a single skin pocket or stiffener

• Biot sidewall/trim slice

• Anechoic reverb TL simulation




FEM to SEA Cross-over in Aerospace Applications

SEA is the primary

integration tool

Includes effects of:

• Sources

• Insulation

• Damping

• Structure

• Absorption

• Leaks

With support from

FEM/BEM

Airplane Half-Ring Model

Lab TL Panel Model

30 to 200+ subsystems




A n e c h o i c c h a m b e r

G r o u n d g r o u n d

r e v e r b e r a t i o n r o o m

i s o l a t o r s

a n e c h o i c c h a m b e r

. . . . .

t e s t a r t i c l e Pi Pr

FEM/BEM Application Example

Transmission Loss

Transmission Loss Test Facility

anechoic chamber

isolators

Test

article

reverberation room

Damping verification, Transmission Loss

• Don’t model chambers, just panel Indirect BEM,

Baffle, Diffuse Source





Flat Panel Transmission Loss Validation

TL Comparison--SYSNOISE vs. Textbook Results

Beranek Noise & Vibration Control Page 307: 5ft x 6.5 ft x 1/8 in panel

(a) reference mode calc. (b) plateau calc. (c) force wave calc. (d) experimental results

0

10

20

30

40

50

60

20 40 80 160

315

630

1250

2500

5000

1000

0

2000

0

Frequency

Tra

nsm

issi

on

Lo

ss

SYSNOISE





Transmission Loss Validation

f = 100 Hz

Structural model Acoustic model

Link

f = 223 Hz




0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

200 1000

Frequency (Hz)

TL

(d

B)

Sysnoise trim

Test trim

Sysnoise bare

Test bare

3” 3I Fiberglass

0.067 Septum

Lining Panel


Transmission Loss Validation




FEM/Modal/IRDM Application Example

Damping Estimations

Detailed FEM

Modal Strain

Energy

Material Loss

Factor System Damping

(Modal)

Synthesized FRFs System Damping

(Band-Average)

0

0.005

0.01

0.015

0.02

0 100 200 300 400 500

0

0.005

0.01

0.015

0.02

100 1000 10000

IRDM Analysis

Modal Damping

Band Average Damping




Application Example - Damping

Define SEA Loss Factors Through FEM

0

0.05

0.1

0.15

100 1000 10000

Insul+Add-on

0

0.05

0.1

0.15

100 1000 10000

Insulation

0

0.05

0.1

0.15

100 1000 10000

Add-On

35

40

45

50

55

60

65

70

75

80

85

90

95

10 100 1000 10000

So

un

d P

res

su

re L

eve

l, S

PL

- d

B r

e 2

0 m

Pa

Loss Factor-1

Loss Factor-2

Loss Factor-3

10 dB




FEM Application Example – Automation/Components

Acoustic Muffler Tool

0

10

20

30

40

50

60

70

80

0 500 1000 1500 2000 2500 3000 3500

FrequencyT

ran

sm

issio

n L

oss

GUI

Reactive

Perforate

Absorbent Combination




Automation of the design process

Physics based models

Conceptual Airplane

Automated model

airplane creation (SEA, FEM, ECS, Ramp)

EBDtrimdens(9%)

UpperNCTL2(51%)

TrimUpThk(36%)

Other(4%)

Anova information for response dBavar

TrimLoThk(40%)

OrthotrimDens(13%)

EBDtrimdens(8%)

UpperNCTL2(5%)

septsurfmass(5%)

TrimUpThk(26%)

Other(3%)

Anova information for response weightvar

Optimization

Component

Performance

Confirmation

Sound Quality and

Regulatory based

Design Objectives

Component

and Parts

Specifications

Use for high pay-off,

redundant and error prone

processes

Muffler tool

SEA Support – Damping,

TL test simulation




Summary and Challenges

Summary • Accurate source modeling critical for aerospace acoustic and structural-acoustic

applications

Future challenges • Verify

Lab

1. Partially correlated sources approximations

2. Improve treatment measurement techniques

Lower/quantify manufacturing tolerances

Component model validation

• Simulate

Improve modeling accuracy and speed

Efficient integration of all methods – FEM, SEA, databases

• Fly

Improve in-flight measurements for (1) better source representations (2) path analysis


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Penn State 2012 Center for Acoustics and Vibration Workshop · Title: Boeing Weston Penn State CAV...

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