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New Advances of Acoustic Simulation Technologies for Aero / Defense IndustriesZe Zhou
FFT / MSC
Free Field Technologies
• Founded in 1998, joined MSC Software in 2011
• Headquartered in Brussels, Belgium
• Activities:
• Development of the Actran software
• Services support, training, consulting & technology transfer
• Research in acoustic CAE and related fields
• More than 300 industrial customers worldwide
Actran Across Industries
Themes of Acoustic / AeroAcoustic Simulation
• Trends in (Aero)Acoustic Simulation:
• Boundary elements , Finite elements Discontinuous Galerkin (DG)
method
• Larger problems, higher frequencies
• Higher Mach numbers
better sources generation, better acoustic propagation !
The Actran Software Suite
Actran Acoustics
Actran Vibro-Acoustics Actran Aero-Acoustics Actran TM
Actran for Trimmed body DMPActran SNGR
ActranVI
Actran DGM
From Actran FEM to Actran DGM
• Actran DGM solves the Linearized Euler Equations LEE (including the energy equation)
• Non-uniform and Rotational mean flow can be addressed
• Non Isothermal mean flow are take into account
• Acoustic Pressure, velocity and density are independently resolved
Navier-Stokes equations
EULER
viscous shear stress
thermal conductionare ignored
Actran DGM
Actran FWH / FEM ( potential flow)
Irrotational flow
Isentropic flow
5 Unknowns per node (Velocity, pressure & density)
Frequency DomainTime Domain
Rotational flow
Actran DGM (Discontinuous Galerkin Method)
• Actran DGM Solving LEE
• Time domain solver, results in frequency domain
as well
• High order elements: 1- 16
• Automatic elements order selection and time stepselection
• Features:
• Propagation in rotational flow, boundary layer flowand supersonic flow
• Massive scale problem / high freq problems
• Highly scalable and GPU acceleration
Sketch of location of degrees of freedom. Dofs are duplicated at the element inte
rface.
History of the Exhaust Noise at Airbus
• Actran DGM is used at Airbus since 6 years in R&D context
• It solves the Linearized Euler Equations (LEE) in time domain.
• It computes acoustic propagation through rotational steady mean flow
2D axisymmetric simulation3D simulation CROR Near-field Noise
FFT acoustic conference 2014, Simulation of installation effects of aircraft engine rearward fan noise with Actran/DGM, J-Y. Suratteau
Time
Airbus - Installation Effects of Aircraft Rear Fan Noise
Challenge
Simulations of large scale domains including flow effects such as the acoustic radiation from turbofan engine installed on the aircraft.
MSC Solutions
Actran DGM is used for computing the far fieldnoise taking account of shapes of engine, wingand pylon. The acoustic propagation accounts for the mean flow computed by steady RANS simulations.
Value
Good correlation with measurements on a canonical test-case (gaps of 1dB). Actran DGM shows a very good computational efficiency and can be used in an industrial context.
AIAA Conference, Simulation of Installation Effects of Aircraft Engine Rear Fan Noise with ACTRAN/DGM, A. Mosson, D. Binet, J. Caprile
Main acoustic phenomena to simulate
pressure real part – mode (13,1)
RANS Flow around the engine Model: engine, pylon, part of the wing
Installation effect (wing effect) above the wing (0H) and below the wing (6H)
Actran DGM for APU Noise at Ground ICAO Regulation for Ramp Noise
• Actran DGM for noise @ ground with a realistic APU exhaust mounted on a A30X Aircraft
• Numerical Model :
• 8500 m3
• 1000 Hz
• 22 CPU hours on 64 procsJet at APU exhaust
Ground/Fuselage InteractionICAO Norm
SPL at microphones
* Aircraft geometry inspired by A30X AIRBUS single aisle aircraft project
Actran DGM – Support of Supersonic Flows
• What: Acoustic propagation in flows with M>1 in Actran DGM
• Targets:
• Exhaust of turbo-engines
• Acoustic propagation in supersonic jets
• Supersonic vehicles (e.g. aircrafts, space launchers…)
• Key Benefits:
• More accurate physics representation
• New applications fully addressed
Exhaust propagation from space launcher travelling at M=1.5
Actran DGM – GPU Acceleration
• Typical Application in aero-engine:• Exhaust noise propagation
• 130M DOFs
• Low memory (6GB) and GPU acceleration
AeroAcoustic Source Generation: Acoustic Analogies
13
Lighthill Analogy
14
Lighthill Analogy & Mohring Analogy
15
Actran DGM with Thompson boundary condition
• What: Support of the integration mapping
method for Thompson BC
• Targets: Propeller noise, Open Rotors noise
• Key Benefits: Time and model complexity
reduction due to coarser DGM elements and bigger time step
CROR acoustic propagation – Image curtesy of Airbus
Actran DGM :Thompson Boundary Surface for Sources
• In Actran DGM:
• The Thompson boundary condition allows to provide realistic solutions at the boundary and at the same time provides a non-reflected behavior
• Requires velocity, density and pressure on a surface at each time step of an unsteady CFD
Linearized Euler Equation
Variational formulation of the Linearized Euler Equation
The Thompson boundary condition feed the surface contribution
Roadmap of Further Developments for Actran DGM
• Aeroacoustics volume sources (Lighthill
Analogy) in Actran DGM will be available in
2017
18
DGM
FEM
SNGR: Stochastic Noise Generation and Radiation
• What: Stochastic Noise Generation and Radiation (SNGR) delivers acoustic results based on inexpensive RANS CFD simulation
• Targets: Aero-acoustic applications where unsteady CFD can be computationally expensive (e.g. wind noise, landing gear, side-mirrors, HVACducts)
• Key Benefits: Computational time reduction for synthetic source computation
Acoustic
Sources
Acoustic Radiation
Unsteady CFD
Engineering Timeline
Actran
SNGR
Actran SNGR & DMP
Steady RANS
CFD
Acoustic Radiation
StandardCAA
SNGRSNGR4 DMP
CFD 345 10 10Actran 5 50 12.5Total 350 60 22.5
Introduction to Actran SNGR
• SNGR Principles• Based on RANS input
• Synthesize turbulent velocity fields used for the CAA Lighthill sources computation
RANS
Mean flow
Turbulent statistics
Tu
rbu
lent S
pe
ctr
um
)(kE
Random number
generatorV
on K
arm
an -
Pa
oU
ser
Def
ined
ExperimentalLES based
or
SNGR: HVAC Demo case
• Example : Computation of Deltas dB on HVAC configurations
• Test Case : Simple 90°duct without and with flap
Flow Inlet
Flow Inlet
Without Flap
With Flap
RANS (k-ε) DES
SNGR: HVAC Demo case
• Delta dB of the Average Pressure at Microphones Placed in Far Field :
• Performance Comparison (with flap model) :
• CFD : RANS : 2.5 MCells / DES : 4.5 Mcells (32 parallels)
• CAA : 980 KDOFs
10 dB
RANS Unsteady CFD Sources Acoustic
RANS Actran SNGR Acoustic
Actran Aeroacoustics
Actran SNGR
SNGR is 5.8 Times Faster for predicting relative levels!
Analytical Fan Noise Sources
• What: Dipole/Monopole-based blade noise model based on Amiet(1) and Dierker(2) models
• Target: Low speed fan noise applications
• Key Benefits:
• Analytical fan noise model (axial and centrifugal)
• Fast design of fan noise applications
(1) R. K. Amiet, Acoustic radiation from an airfoil in a turbulent stream, JSV, 1975(2) Dierke, J., et al, Installation effects of a propeller mounted on a wing with Coanda flap. Part II. Atlanta, USA , 2014. 20th AIAA/CEAS. 3189
Non-Parametric Variability Method (NPVM)
• What: Non-deterministic approach in Modal Frequency Responses through a Monte-Carlo solution framework
• Targets: Aerospace & auto vibro-acoustic applications
• Key Benefits:• Extension of Actran capabilities in the mid-frequency
range• Access to the dispersion of vibro-acoustic responses
BEGIN PARAMETERNUMBER_SAMPLES 20
END PARAMETER
BEGIN COMPONENT 1MODAL_ELASTICDOMAIN Structured_mesh1MODES_FORMAT OP2FIRST_MODE_INDEX 0…NON_PARAMETRIC_VARIABILITY_STIFFNESS 0.05NON_PARAMETRIC_VARIABILITY_MASS 0.05NON_PARAMETRIC_VARIABILITY_DAMPING 0.05
END COMPONENT 1
NPVM implementationCh. Soize, A nonparametric model of random uncertainties for reduced matrix models in structural dynamics, Probabilistic Engineering Mechanics, 15, 2000
Step 2 – Energy distribution in different patchesStep 1 – Automatic Model Patch partitioning
Energy Analysis
• What: Energetic post-processing of large/high frequency structural models
• Targets: Automotive and aerospace structural applications
• Key Benefits:
• Finite-element-based energetic analysis
• Handling of results on a patch level when local results are less relevant (e.g. on large models and/or at high frequencies)
Adaptivity capabilities – Overview
• What: Adaptive meshing technology (H-Adaptivity) to:• Structural surface elements;• Equivalent fluids / porous components
• Key Benefit: Important reduction of the Actran model build time, meshing effort thanks to optimized meshes for the given frequency range
Low frequency mesh High frequency mesh
Perforated Plates with Structural Deformation
• What: Take into account the effect of perforations on the structure behavior as well as its flexibility
• Targets: Shell noise for exhaust applications, automotive mufflers and others
• Key Benefits:
• No requirement to mesh the perforations
• Improved accuracy of vibro-acoustic models including perforated plates Muffler with perforated shell between the centra
l duct and the external cavity
Perforation material definition with shell material
Aircraft Ventilation SystemSOFTAIR French Project
Challenge
Define, propose and validate an optimal acoustic treatment for an air conditioning plenum.
The validation shall be performed between measurements and calculations in flow and no flow condition ona test bench.
MSC Solutions
Actran & Patran have been linked together for definingDOE on several acoustic treatments.
Value
Very Good correlation with measurements has been achieved. Large range of configurations have been simulated to help finding the optimal one.
Acoustic treatment modeled in Actran
NIDA and Wiremesh definition in Actran
Pressure ratio (real part) upstream / downstream the treatment:Measurements Vs Actran
Acoustic pressure calculated in a duct with treatment
Treatment
CRESCENDO - European FP7 Project on Aircraft Noise Optimization by Simulation Engineering
Challenge
Considering noise issues at design phase of aircraft equipped with CROR engines
FFT/MSC Solutions
1. SimXpert: Nastran structure modeling
2. Nas2Act: converting Nastran model into Actran model
3. Actran: enriching the Actran structure model with fluid, foam materials and non-uniform pressure excitation (ONERA) on the fuselage
Value
Compute sound pressure level in the cabin due to airborne excitation of synchronous and asynchronous engines
Wizard for Space Vibro-Acoustic Applications
• What: Wizard to generate the acoustic model step-by-step, including mesh generation.
• Targets: Space components subjected to diffuse sound field
• Key Benefits:
• New & Unexperienced users: guidance through the complete process
• Expert & Experienced users: accelerates the operation
Set Analysis Parameters
Import Structure modal basis
Create Acoustic mesh
Apply Diffuse sound field excitation
Specify Outputs
Valuable output for acoustic loading dimensioning (e.g. acceleration, stress, strain, etc.)