Seminar acoustic engineering marineindustries

Handzettel 1

Unrestricted © Siemens AG 2014 All rights reserved. Smarter decisions, better products.

Acoustic Engineering Simulationfor the Marine Industries

Siemens PLM Web Seminar – 25.02.2015

Ir. Peter SEGAERT – Siemens PLM STS 3D – Leuven, Belgium

2014-06-17

Unrestricted © Siemens AG 2014 All rights reserved.

Page 2 Siemens PLM Software

Presentation Contents

Vibro-Acoustic Simulation Process

Intro STS - Noise & Vibration in Shipbuilding

2

Application 1 : Ship Hull Radiation3

Application 2 : Acoustic Signature4

1

Advanced Engineering for Marine Industry - Slide 2

5 Application 3 : Propeller Noise

6 Application 4 : Sonar Arrays

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Worldwide leader in functional performance engineering for transportation industriesAutomotive – Aerospace – Railway – Shipbuilding– Agricultural, Construction & Off-road

Serving more than 100.000 R&D engineers … in 5.000 manufacturing companies

Top talent in 45+ offices worldwide… 1.400 professionals

Previously known as LMS, now business segment STS = Simulation and Test Solutions of Siemens PLM Software since 2013

Our vision : “Closed-Loop Systems Driven Product Development”

Siemens PLM STS = +30 years of Engineering Innovation in Test & Mechatronic Simulation

55 %

25 %

20 %

Beijing

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Kaiserslautern

Madrid

Leuven

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Toulouse

Plymouth

Roanne

Torino

Yokohama

R&D & Engineering

Centers


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Test-based Engineering (modal, NVH, acoustics, durability)

Mobile, Laboratory

LMS SCADAS

Product Design Controls Engineering3D Simulation

Mechatronic System Simulation

System Synthesis System Data Management Multi-physics Modeling

PLM STS Product Range = Closing the Loop between Simulation & Physical Test


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3D Simulation SolutionsCAE Software Suite for Multi-attribute Simulation

Acoustics & VibrationProcess Integration

AutomotiveMechanisms

• LMS Virtual.Lab Acoustics• LMS Virtual.Lab Noise & Vibration• LMS Virtual.Lab Correlation

• LMS Virtual.Lab Motion• LMS Virtual.Lab Durability• LMS Samtech TEA Pipe

• LMS Virtual.Lab Structures

Process Integration Aviation

Wind TurbinesStructural Analysis

• CAESAM • LMS Samtech SAMCEF• LMS Samtech Mecano• LMS Samtech Rotors• LMS Samtech Composites

• SAMCEF Wind Turbines


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Acoustic Comfort

• Work environm.• Crew cabins

Industry solutions

• Decoupling machinery

• Silent equipment

• Damping materials

Hull Radiation

• Water loading effect on dynamics

• Directivity patterns

Industry solutions

• Estimate added mass effect


N+V Transmission

• Vibration paths• Sound paths

Industry solutions

• Engine room shielding

• Transfer path reduction e.g. elastic couplings

Ship Engine

• Engine radiation• Intake/exhaust

noise

Industry solutions

• Reducing engine vibrations

• Flexible mounts

• Decoupling connections to main structure

Part 1 – Noise & Vibration in Shipbuilding

N+V Issues in Ship Design & Engineering (1)Advanced Engineering for Marine Industry - Slide 6

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Sonar Design

• Ships• Submarines• Mines

Industry solutions

• Sonar arrays

• Sonar domes

• Towed sonars

• All around sonars

Propeller Noise

• Noise from blades• Cavitation

Industry solutions

• Geometric design of propeller blade shape

• Propulsor ducts

Acoustic Scattering

• Stealth properties

Industry solutions

• Anechoic surface tiles (rubber or neoprene)

Acoustic Signature

• Hull radiation• TBL noise

Industry solutions

• Decoupling of machinery

• Anechoic tiles

• Improved hydrodynamics


N+V Issues in Ship Design & Engineering (2)Advanced Engineering for Marine Industry - Slide 7

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Overview of Frequency Range

• Noise & vibration sources in ships cover a large frequency range, from a few Hz for hull vibrations, up to 10 kHz and higher for cavitation


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STS customers in Shipbuilding Industry (1)

• RUSSIAN FEDERATION : KRYLOV Shipbuilding ; RUBIN Design Bureau ; ATOLL Scientific Research Institute

• AUSTRALIA: ASC (Australian Submarine Corp)

• UNITED STATES : MERCURY Marine; LOCKHEED-MARTIN ; NORTHROP-GRUMMAN shipyard ; BOMBARDIER Outboard Marine ; Boston Whaler ; US Naval Postgraduate School

• JAPAN: KAWASAKI Shipbuilding Corp ; YAMAHA Marine ; MITSUBISHI Heavy Industries ; Japan Defense Agency

• KOREA: ADD (Agency for Defense Development) ; HYUNDAI Heavy Industries ; DOOSAN Heavy Industries & Construction ; SAMSUNG Heavy Industries

• SINGAPORE: DSO (Defence Science Organization)

• ITALY: FINCANTIERI [Cantieri Navali Italiani spa] ; CETENA

• FRANCE: THALES Underwater Systems (sonar systems) ; DGA ; INRS ; DCNS Lorient (French Navy shipyard) ; Bassin des Carenes (ship hull naval research centre)


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STS customers in Shipbuilding Industry (2)

• GERMANY: THYSSEN-KRUPP Marine ; Germanischer Lloyd ; HDW [Howaldtswerke – Deutsche Werft] ; MEYER Werft ; FWG Kiel

• NETHERLANDS: Koninklijke Marine

• UNITED KINGDOM: QINETIQ ; FRAZER-NASH Consulting ; THALES ; BAE SYSTEMS

• PR CHINA: Shanghai Marine Diesel Engine Research Institute ; Institute 726 ; Institute 715 ; Institute 701; Inst719 ; Inst702 ; Inst704 ; Institute 703 ; HARBIN Engineering University


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Part 2 — Vibro-Acoustic Simulation Process

The Source – Transfer – Receiver Model (1)

Acoustics = study of generation, propagation and reception of compressional waves in an elastic medium (fluid or solid)


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The Source – Transfer – Receiver Model (2)

Sound Source

EM forces

ReceiverSystem Transfer

Flow-inducedpressurefluctuations

Test data

Mechanicalvibrations

FEM Vibro-Acoustics

BEM Vibro-Acoustics

RAY Acoustics

Standard

Advanced


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The Philosophy — Data Flow SequenceAdvanced Engineering for Marine Industry - Slide 14

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In Real Life — LMS Virtual.Lab Process FlowAdvanced Engineering for Marine Industry - Slide 15

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Low freq ?or

High freq ?

Harmonic ? or

Transient ?

Interior ?or

Exterior ?


Acoustic Simulation : four main questions !

Uncoupled ?or

Coupled ?


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Time-domain Acoustics : wave equation

Acoustics = scientific study of generation, propagation, and reception of sound waves

What is sound ??• Small amplitude variations of pressure & density of an elastic medium (air,water)

around equilibrium values• Propagation = longitudinal compression/rarefaction waves

Mathematical description = linear wave equation

• Wave propagation with sound speed c = [dp/d1/2

• Time domain description• Contains all usual wave phenomena : refraction, reflection, diffraction

01

2

2

22

t

p

cp


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Frequency-domain Acoustics

Time-domain wave equation => Fourier transform => Frequency-domain equation

p = complex pressure k = /c = wavenumber

Helmholtz equation• Frequency domain description - fully equivalent to wave equation• Second-order linear partial differential equation

Covers all possible acoustic situations• Interior acoustics = bounded domains• Exterior acoustics = unbounded domains• Interior/exterior combinations

• Presence of holes and openings• Transmission

0~~ 22 pkp


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Acoustic Configurations

Cavity acoustics (interior)

Sound radiation (exterior)

Reflection/diffraction (exterior)

Sound transmission (exterior/interior)


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FEM/BEM Fundamentals (1)

Finite Element Method Boundary Element method

• Higher modeling effort : 3D mesh Lower modeling effort : 2D meshdiscretization of fluid volume discretization of surface

• Modal-based approaches possible No modal-based approach

• Sparse matrices = Dense matrices =faster computation longer computation

• Heterogeneous fluid Homogeneous fluid only


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FEM/BEM Fundamentals (2)

BEM – Boundary Element Method for exterior acoustic radiation simulation

Modeling effort = only boundary mesh representation needed

Accuracy = Sommerfeld radiation condition at infinity is guaranteed by use of Green’s kernel function in BEM formulation -no radiated power will be reflected from infinity

FEM – Finite Element Method for exterior acoustic radiation simulation

Modeling effort: = for exterior radiation, you need engine boundary representation + an outer boundary limit for the FEM domain + fill volume in-between with fluid elements

Accuracy = to satisfy the Sommerfeldradiation condition, a ‘treatment’ has to be applied at the outer FE mesh boundary to model the unboundedness of the volume around the vibrating structure, i.e. to ensure that no sound waves are reflected from the FE mesh outer boundary


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Pros and Cons of Acoustic FEM

• PRO - Acoustic FEM supports acoustic medium with heterogeneous properties

• Temperature gradients and density gradients(e.g. as occur in exhaust gas systems or water depth in underwater acoustics)

• Convection of sound waves due to high-speed main flow

• PRO - Acoustic FEM supports definition of bulk absorbing materials

• Mineral wools & foams as volume absorbers

• Modeling of poro-elastic absorption properties

• PRO - Acoustic FEM supports acoustic modal analysis

• PRO - FEM matrices have a sparse structure

• More speedy resolution than BEM, where matrices are dense


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Pros and Cons of Acoustic BEM

• PRO - Boundary Element mesh is a surface-type mesh

• Easier and faster modeling compared to FEM volume-type meshes

• Direct usage of an existing structural mesh• Removal of small details (ribs) using VL Mesh Coarsening• Remeshing with different mesh size using VL Mesh Coarsening

• PRO - Natural handling of typical acoustic configurations

• Unbounded (infinite) domain for acoustic radiation problems(FEM requires Infinite Elements or PML/AML formulation)

• Openings, holes, etc… do not require special handling(FEM requires equivalent impedance boundary conditions)

• CONTRA – Boundary Element Method requires homogeneous medium

• Different fluids are not allowed (e.g. water and air in the same model)

• Single-fluid medium cannot have strong temperature or density gradients


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Max Frequency Determines Element Size

Maximum frequency criterion for wave simulation• N elements required per wavelength l, in order to

have an accurate representation of wave shape

• Typical values : N=6 to N=10

There is a strong connection between frequency range and element size : higher frequency means smaller element size, means more elements.

This puts a practical upper limit on the frequency range : the larger the object, the lower the max analysis frequency will be.

max6 f

ch

Field variation in space

Fie

ld a

mp

litu

de


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Max Frequency applied to FEM-BEM

Model size (number of nodes) of discretization methods grows with frequency

• BEM n ~ f^2• FEM n ~ f^3

Computation times scale with number of nodes• Conventional BEM ~ O(n^3)• Fast Multipole BEM ~ O(n log^2(n))• Conventional FEM ~ O(n*b^2)

• …….Computation times become prohibitive at higher frequencies!

However, several applications require support for:• High frequencies: study of audio system acoustic performance

requires covering the full audible frequency range

• Large sizes: airplanes, trains, ships and submarines, architectural acoustics

1 kHz BEM

18 knodes

4 kHz BEM

288 knodes

2 kHz BEM

72 knodes


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Max Frequency : Large diesel engine example

Due to the size of the model, 3 Boundary Element models have been considered, the calculation process has been executed for each of them

0 – 1 kHz 1 – 2 kHz 2 – 3 kHz


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Acoustic Comfort

• Work environm.• Crew cabins

Industry solutions

• Decoupling machinery

• Silent equipment


Hull Radiation

• Water loading effect on dynamics

• Directivity patterns

Industry solutions

• Estimate added mass effect


N+V Transmission

• Vibration paths• Sound paths

Industry solutions

• Engine room shielding

• Transfer path reduction e.g. elastic couplings

Ship Engine

• Engine radiation• Intake/exhaust

noise

Industry solutions

• Reducing engine vibrations

• Flexible mounts

• Decoupling connections to main structure

Part 3 — Ship Hull Radiation

Ship Hull Radiation & Added Mass EffectAdvanced Engineering for Marine Industry - Slide 28

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General Remarks

Objective Predict the noise field radiated from the hull due to machinery vibrations : engines, pumps, motors, electrical generators, etc.

Analyze the signature:

-Directivity patterns

-Structure-borne versus airborne contributions

-Identify structural modes particularly radiating

Design proper countermeasures:

-The right mounts

-Location where to modify structure

-Fitting of anechoic tiles to the hull

Particular issues

Dynamics of the ship’s structure are changing when immersed in water - structural resonances are changing to lower frequencies due to water loading

Waterline is dependent upon ship loading conditions and water temperature => different cases to consider


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Hull Radiation - Physical ViewpointAdvanced Engineering for Marine Industry - Slide 30

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Hull Radiation - Simulation ViewpointAdvanced Engineering for Marine Industry - Slide 31

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Structural FEM coupled to Acoustic BEM (1)

Solution Virtual.Lab Boundary Element Acoustics

Benefits Accurately and efficiently models the water loading start from ‘dry structural modes’

Assess directivity patterns

Creates insights (path contribution, panel radiation,…) link mount forces to acoustics

Efficiently change the waterline

FEM Mesh

BEM Mesh

Modes

Radiation

Acoustic-structural coupling


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Model Courtesy of IABG

Objective:• compute the acoustic field radiated by the

shell of the ship

Modeling:• a boundary element mesh of the immersed

part of the ship• a structural finite element model of the ship• Infinite free surface (sea level)

Computation:• Fully-coupled approach

Sound propagation in water: radiation due to structural vibration


Structural FEM coupled to Acoustic BEM (2)Advanced Engineering for Marine Industry - Slide 33

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Automatic mapping from structural to acoustic mesh

Structural FE Model• Contains volume elements• Structural modal basis (dry modes)

25 Mode Shapes, up to 25 Hz

Automatic Mesh Coarsening• Replace volumes by their envelope• Clean the surfaces• End with the external shell

Acoustic BEM Model• Only the underwater shell• Wetted on one side only (Direct or Indirect BEM)• Free half-space plane (p=0)• Map ‘finer’ structure onto ‘coarser’ acoustic

mesh Mesh mapping Modes mapping



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Radiated sound field

Results (mode #9 - 8 Hz):• The structural deflection on the ship, including coupled modes (added mass effect)• The underwater field radiated by the shell.

Design changes? Structural modification (change the modes)

Mechanical isolation (reduce the excitation)

Acoustic treatment (decouple the radiation)



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Structural FEM coupled to Acoustic BEM (5)

Analyze noise with and without water loading: inspect mode shifting

Analyze directivity patterns

Colorbar displays to identify efficiently critical areas

Acoustic Power Analysis


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Example : Hyundai Heavy Industries

Challenge The customer is experiencing problem with the ship sonar

operation because of high underwater tonal noise from ship engine. Need to improve design to reduce noise radiation

Solution LMS Virtual.Lab NVH to analyze energy transfer path from engine

vibration to noise radiation LMS Virtual.Lab Vibro-Acoustics to evaluate the effect of an

additional damping structure

Result: Customer was able to design the damping and absorptive system

to reduce hull vibration and noise radiation by 10 dB

Source:

B. H. Yoo, J. H. Park W. H. Joo and K. D. Lee:

“Numerical Analysis and Practical Proposition to Reduce Underwater Radiated Noise from Submerged Hull”,

Inter-Noise 2004, Prague, Czech Republic, August 22-25, 2004.


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Model Courtesy of QinetiQ

Reference: ICSV11 Conference, 2004


Example : Torpedo Hull Radiation (1)

Features• Heavy fluid = water• Fully-coupled fluid-structure interaction• Acoustic source at large distance• Test using reciprocity principle

Objectives• Radiation due to internal force• Experimental verification


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Example : Torpedo Hull Radiation (2)

Fully-coupled approach• Structural flexibility included• Modal model of structure• Interior acoustic ‘void’ with structural elements (only exterior

wetted)• Acoustic BEM coupled solution

Acoustic BEM mesh

+ Structural mode shapes

BEM Coupled solution

(structural forces)

Acoustic

Radiation field


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Experimental Verification (1)

Reciprocity Principle• Open-water test facility• Acoustic source• Structural response measurements (v)

Structural Correlation• Modal analysis in air• Modal correlation / updating

Hydrosounder

Hydrophone

Cylinder

Water surface

16m

1mSupport

forcylinder

QStrengthSource

vVelocity

FforceExcitation

ppressurefieldFar

,

,

,

,

Model Experiment


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Experimental Verification (2)Advanced Engineering for Marine Industry - Slide 41

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Experimental Verification (3)

20 dB


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Sonar Design


Industry solutions

• Sonar arrays

• Sonar domes

• Towed sonars


Propeller Noise


Industry solutions


• Propulsor ducts

Acoustic Scattering


Industry solutions


Acoustic Signature


Industry solutions


• Anechoic tiles


Part 4 — Acoustic Signature

Acoustic Stealth & Sonar ScatteringAdvanced Engineering for Marine Industry - Slide 44

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Acoustic Stealth

Objective Make the ship or submarine more ‘stealth like’

Analyze the scattered field:

-Minimize the reflected field

Design proper countermeasures:

-Fitting of anechoic tiles to the hull

-Shape

From low to mid frequency sonar wave excitation

Particular issues

Effects of the flexibility of the ship on the scattered field

Sound waves hitting from different angles


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Objective: Optimize the acoustic signature of the submarine (frequency response), scattered

field

Modeling: Structural FEM modal model plus physical BEM acoustic model Interior ‘void’ in acoustic model (no fluid) Acoustic source at large distance: Incident plane wave, arbitrary angle

Computation:

Fully-coupled approach >< Uncoupled approach

Model Courtesy of IABG

Sound propagation in water: scattering of incident sound wave


Scattering of Sound from a Rigid/Flexible Submarine


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Scattering with Acoustic BEM

Solution Virtual.Lab Boundary Element Acoustics

Benefits Analyze the scattered field from different angles efficiently

Efficiently run and analyze different designs and different loading conditions

BEM Mesh

Incident wave


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Scattering with Acoustic FEM

Solution Virtual.Lab FEM AML - Virtual.Lab FEM Acoustics

Benefits Analyze the scattered field from different angles efficiently

Efficiently run and analyze different designs and different loading conditions

FEM Mesh with AML Property

Incident wave

FEM

analysis


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Sound Field Results at 1000 Hz

Total pressure field for plane wave excitation

Scattered pressure field


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Influence of Surface Treatment

Scattered pressure field WITH surface treatment (sound absorbing tiles)

Scattered pressure fieldwithout surface treatment


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Rigid versus Flexible Analysis

Rigid Frame Flexible Frame

Effect of the flexibility of the structure take into account in the scattered field


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Sonar Design


Industry solutions

• Sonar arrays

• Sonar domes

• Towed sonars


Propeller Noise


Industry solutions


• Propulsor ducts

Acoustic Scattering


Industry solutions


Acoustic Signature


Industry solutions


• Anechoic tiles


Part 5 — Propeller Noise

Sound Field from Propellers using CFDAdvanced Engineering for Marine Industry - Slide 53

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E.g. torpedo, submarine or other systems

Objective Predict the noise radiated by the propeller :

Tonal noise component; multiple of Blade Passing Frequency (BPF)

Propeller is a major component of the acoustic signature. The circumferential variation on Axial Instream Velocity causes harmonic loading content for the blades 1st public display

of submarine propeller

CFD path lines


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Propeller Noise Classification

Propeller Noise

Non Cavitating Cavitating

Blade Tonals (RPM * n blades * m) NOT POSSIBLE

Broadband NoiseDue to turbulence and trailing edge vortices NOT POSSIBLE

Propeller SingingIn case vortex shedding frequency corresponds to the blade resonance frequency NOT POSSIBLE


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Technical base = Aeroacoustics

Solution Virtual.Lab Boundary Element Acoustics - Virtual.Lab Aero-Acoustics

Benefits Timely prediction of flow-induced noise for every design loop

Exploits at best the complementarities between low-order CFD and acoustic propagation codes

Unique approach on the market, enforcing the correct radiation characteristics of the source region

Find possible noise issues and suggest design improvement

Convert to Lighthill equivalent Fan sourceBEM / FEM propagation

CFD calculation on propeller

BEM or FEM mesh of structure


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AeroAcoustic Sources (Lighthill analogy)

Unsteady Flow

Moving Surfaces

Steady Surfaces

No Surfaces

(or smooth surfaces)

Quadrupoles

Dipoles on surfaces + Quadrupoles in wake

Rotating Dipoles + Quadrupoles in wake


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Part 5 — Propeller NoisePropeller coupled response to structural excitation -Underwater radiation pattern


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Adobe Acrobat Document


Some Academic References

Non-uniform flow conditions into thepropeller cavitation; prediction andvalidationQiong Yang Fang ; Wang YongshengNaval Ships and Power EngineeringWuhan University

Adobe Acrobat Document


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Sonar Design


Industry solutions

• Sonar arrays

• Sonar domes

• Towed sonars


Propeller Noise


Industry solutions


• Propulsor ducts

Acoustic Scattering


Industry solutions


Acoustic Signature


Industry solutions


• Anechoic tiles


Part 6 — Sonar Arrays

Analysis of Sonar Transducer ArraysAdvanced Engineering for Marine Industry - Slide 61

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SONAR Transducer – Solution Process

2. Vibroacoustic field solution with the Direct Nodal BEM or with FEM PML/AML

• Computes the full coupled acoustic field and the structural excitation: field potentials and modal participation factors

• Exports modal part. factors to *.unv file to ATILA

ATILA FEM

Compute structural dynamics

Virtual.Lab Acoustics: Compute coupled

vibroacoustic field solution

1. Structural modal solution with the Finite Element Method

• Computes the ‘dry’ structural modes: shapes, frequencies, forces

• Exports modes to *.unv file to Virtual.Lab

3. Electromechanical interaction

• Takes the modal participation factors from Virtual.Lab

• Computes the electric field and structural displacements/stresses


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Example 1 – Piston piezo-electric transducer Comparing DBEM and FEM AML

Comparison between Atila –Virtual.Lab DBEM and Atila –Virtual.Lab FEM AML for a piston piezoelectric transducer (length x diameter = 40 mm x 8 mm) fully immersed. Resonance frequency at 25 kHz.

DBEM

FEM AML

Deviation in directivity: max 0.2dB


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ATILA/Virtual.Lab FEM AML simulation of• Single piston transducer• Six elements array with front plate

• Maximum response frequency changes from 101 kHz to 95 kHz

• Directivity shows considerable adjustment


Example 2 – Side scan sonar arraySingle element versus 6-element array

Stress and displacement

Transmitted Voltage Response

Directivity

Single piston

Array with front

plate


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DBEM, full immersion


Example 2 – Side scan sonar arrayFull immersion versus one-sided water contact

FEM AML one-sided water contact, rigid baffle

Near field and directivity at 95 kHz


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Example 3 – Multi-beam Sonar ArraySonar beam steering by voltage phasing

5x5 rectangular elements, resonant frequency 42kHzOne-sided water contact: Atila – Virtual.Lab FEM AMLTwo cases: unsteered beam and beam steered at 30°


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