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ACTRAN Vibro-Acoustics

Product overview

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ACTRAN Modules
ACTRAN for NASTRAN ACTRAN DGM

ACTRAN Vibro-Acoustics

ACTRAN Aero-Acoustics

ACTRAN TM

ACTRAN Acoustics ACTRAN VI 2

Copyright Free Field Technologies

ACTRAN VibroAcoustics
? Contains all structural modeling features as well as strong vibroacoustic features of ACTRAN
? Structural finite elements ? Modal representation of the structure’s dynamic behavior ? Mechanical excitations (incl. random excitations) ? Fully coupled solver

? Applications:
? Strongly coupled vibro-acoustic analysis ? Acoustic transmission ? Vibration of structures in a heavy or light fluid ? Multi-domain, multi-physics applications

? Requires

ACTRAN Acoustics
as a pre-requisite ? Is a pre-requisite for:
? ACTRAN for NASTRAN

3

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ACTRAN Acoustics Features
? Based on finite and infinite elements
Import vibration data from Nastran?, Ansys?, Abaqus?… Infinite elements to propagate waves in the far field Visco-thermal losses, various damping mechanisms Rigid porous material Propagation in heterogeneous medium (T and V computed in Actran or imported from CFD codes) ? Fast solvers, multiple load, parallel features ? ? ? ? ?

? Typical results (among other)
? Acoustic pressure, intensity and power ? Power balance statements, waterfall diagrams

? Applications
? Engine: power train, oil pan, manifold, exhaust, … ? Engine compartment insulation ? Any vibrating / radiating component
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Vibro-Acoustics Elements Library
? Acoustic elements
? Can support an heterogeneous medium (a flow field and/or a temperature field, for example) ? Infinite elements

? Shells, solids
? Visco-elastic shells, porous materials, see later ? Visco-elastic solids ? Piezo-electric elements (electric excitation, mechanical response) ? Stiffeners, beams and mass-spring systems

? Automatic computation of local/global indicators
? displacement, acceleration, stress ? mean square velocity, dissipated energy ? Automatic energy balance statements

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Porous Materials…
? Model foam, rock wool, fibers...

? Porous elements: all based on Biot model
? Vibrating skeleton surrounded by a fluid ? Thus 3 + 1 = 4 degrees of freedom per node ? Material properties (frequency dependent):
? Foam skeleton properties : Young modulus, density, Poisson ratio ? Fluid properties : fluid density ? Foam properties : tortuosity, resistivity, porosity, imperviosity…

? Micro-Model developed by Allard-Johnson

? Local & global indicators:
? displacement, pressure… ? dissipated energy in each layer or each material or any specific area defined by the user
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Porous Materials: variants!
? Full Biot – Allard porous u-p formulation:
? ? ? ? u-p formulation, 4 degrees of freedom per node Very complete, very reliable: state of the art! Anisotropic formulation supported in Actran Requires extensive material properties (8 parameters, including tortuosity, flow resistivity…)

? Delany Bazley u-p:
? Well suited if porosity close to 1 (ex: glass wool), in some frequency bands ? Less extensive material properties are needed (4 parameters)

? Simpler models with 1 degree of freedom per node
? Lumped porous, well suited if the skeleton is very soft (added mass) ? Craggs (rigid porous), well suited if the skeleton is almost rigid

? FFT can definitively help you to select the most appropriate porous model in a specific situation
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Excitations
? Standard excitation
? ? ? ? Point loads, displacements Monopoles, plane waves, etc Distributed loads Electric excitations (piezo)

? Random excitation (random fields)
? Diffuse sound field
? Model reverberant room experiments can also be imposed with a series of plane waves

? Turbulent Boundary Layer noise (TBL):
? Corcos & Goody models

? Delta correlated excitation
? Model Rain-on-the-roof excitation

? Computation of mean values and standard deviation of any stochastic quantity
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Solution Schemes & Solvers
? Solution schemes
? Frequency response analysis ? Modal extraction analysis ? Time domain analysis

? Support of non-congruent meshes

? Physical or modal approaches
? Support of existing Nastran? modal models ? Superelements

? Solver
? Efficient direct and iterative solvers ? Fast Frequency Response Krylov Solver ? Advanced parallelism and multi-thread capabilities
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How long does it take? (all models are 3D)
? Loudspeaker, 40cm height, whole freq.band ? 2kHz: 2h

on a laptop
? A320 fuselage slice w/ foam and everything, up to 2kHz:

2h on a standard PC

? Truck engine (2.5 meters long), up to 2kHz, 3 hours on a
small cluster

? Please ask a timing for your application!

11

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Target Applications
? Intake & exhaust system ? Transparency computation ? Trim analysis – component level ? Random vibro-acoustics
? Side window or windshield submitted to a random aerodynamic excitation. ? Satellite and/or its embarked components (antennas, solar array panels…), rocket nozzle, rocket fairing… during launch process ? TBL noise on the aircraft fuselage transmitted to the cabin

? Radiating structures ? Ship building

? ...
? See applications in dedicated presentations
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