FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Industry Sector RTD Thematic Area Date Deliverable NrLand Transport & Aerospace Multi-Physics 13-Nov-01

Finite Element & Boundary Element Technology in Acoustics & Structural Dynamics : Current Status & Key Trends for the FutureIr. Peter SEGAERTLMS International - Leuven, Belgium

SummaryOverview of current FEM/BEM based simulation technology in Acoustics & Structural Dynamics, including obstacles to efficient use and key trends to satisfy needs of automotive & aerospace industries

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

1st FENET Workshop

Wiesbaden [Germany]13-14 November 2001

Finite Element & Boundary Element Technology in Acoustics & Structural Dynamics : Current Status & Key Trends for the Future

Ir. Peter SEGAERTProduct Support Manager - CAE VibroAcoustic Modeling Group

LMS International [Leuven, Belgium] www.lmsintl.com

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

LMS & FENETLand Transport & Aerospace Industry Sector

LMS develops, markets and supports CAE tools in the field of numerical vibro-acoustics based on FEM/BEM technology:

• Acoustics => LMS SYSNOISE• Structural Dynamics => LMS SYSNOISE & LMS GATEWAY• Durability & Fatigue => LMS FALANCS• Motion => LMS DADS• Acoustics, Durability & Motion => LMS VIRTUAL.LAB (next generation software)

Main application fields of these tools are within R&D and Engineering departments of

• Automotive industry OEMs : car, truck & bus• Automotive industry “tier 1” component suppliers• Aerospace industry : aircraft & satellite manufacturers

General perspective from the software industry on • Current practice of FEM/BEM vibro-acoustic codes in industry• Obstacles to effective use of FEM/BEM technology• Industry needs & key trends to satisfy these needs in the future

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What is Numerical Vibro-Acoustics ?

SourceSource PropagationPropagation ReceiverReceiversound path & absorption

airbornestructure-bornemixed

vibrating bodyspeaker

microphoneear

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Why is Vibro-Acoustic Simulation becoming more important ?

Noise reduction and sound quality have become major issues• Important contribution to perceived product quality• Delivering low-noise level products creates a competitive advantage• Government regulations constantly impose lower noise levels in the quest for a

cleaner environment

Analysis can be performed at several levels in the design cycle...• Explaining and understanding the physics behind it• Troubleshooting• Evaluate design alternatives & reduce costly physical prototyping

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Tools for Numerical Vibro-Acoustics

(Semi-) Analytical Methods• Closed form solutions, only for simple geometries

Finite Element Method (LMS SYSNOISE/FEM)• Volume discretization of fluid region

Boundary Element Method (LMS SYSNOISE/BEM) • Discretization of bounding surface only

Statistical Energy Methods• Energy exchanges between system components• LMS SEADS

Ray Tracing Methods • Geometrical Acoustics• LMS RAYNOISE

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Example : SYSNOISE Modular ArchitectureFEM & BEM Methods – Uncoupled & Coupled

KernelKernel

Acoustic FEM

I-FEM

DBEM

IBEM

Struct.FEM

Struct.FEM

Struct.FEM

Struct.FEMH

armonic H

arm

onic

Transient

Transient

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Numerical Vibro-Acoustics : Current Industrial Practice of FEM/BEM-based

CodesApplied in R&D or Advanced Engineering depts :

• “up-front” troubleshooting• “what if” experiments = virtual prototyping to reduce amount

of physical prototypes• gainining insight in the “physics” beyond analytical models

In general, not applied in everyday use as “mainstream”design codes

Typically used for :• component-level analyses• not for system-level analyses• e.g. engine block radiation, oilpan radiation, exhaust

radiation, but not complete powertrain, etc…

Typically lower frequency range or low modal density ranges (from a few hundred up to 2-3 KHz)

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Numerical Vibro-Acoustics : Current Obstacles for More Efficient Use

Large computational effort involved• large matrices, especially in BEM (dense matrices),

requiring large amounts of RAM• each analysis frequency forms an independent problem

=> analysis over a large frequency range can take several days of solving time

High-frequency limit• Maximum analysis frequency linked to mesh refinement

(λ/6 rule), leading to very large meshes for high frequencies

• Control of numerical error propagation at high frequencies

Uncertainty with respect to “impedance” properties of acoustic damping materials

• for many materials, impedance is not known as a function of frequency

Intake model Courtesy of Allied Signal

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Numerical Vibro-Acoustics : Key Trends to satisfy Auto & Aerospace Industry Needs (1)

Reducing computational efforts through novel techniques• Acoustic Transfer Vector [ATV] concept – LMS patent• improving solver technology => importance of fundamental research at

universities + dissemination by FENET

Reducing computational efforts by exploiting networked computers as virtual parallel machines

• “frequency level” distribution for vibro-acoustic problems : multiple processors solve simultaneously for different frequencies => already implemented in LMS SYSNOISE

• introduction of “domain decomposition techniques” or “distributed domain solvers”: each processor resolves part of the solution domain, with appropriate continuity conditions at the sub-domain interfaces

• research work on improving parallel algorithms => role of fundamental research

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Numerical Vibro-Acoustics : Key Trends to satisfy Auto & Aerospace Industry Needs (2)

FE analyst “user profile” is changing over time !• from “FE analysis specialist” to “design engineer doing analysis” => role of

academia and organizations like NAFEMS & FENET to provide continuous education & grounding in best practices

• from “central computer in batch” to “interactive UNIX workstation” to “Windows-based PC platform” user => role of industry to provide adapted software tools

• importance of proper initial training & continuous updating of knowledge cannot be overestimated => role of FENET !

Most significant technical trend in numerical vibro-acoustics is the move towards aero-acoustics :

• flow-induced noise & fluid-structure interaction• interfacing & coupling of Vibro-Acoustic simulation software with CFD software