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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.)

Thank You !Ze Zhou

ze.zhou@fft.be

31

Visit www.fft.be for more info