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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 90duct without and with flap

Flow Inlet

Flow Inlet

Without Flap

With Flap

RANS (k-) 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 0NON_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 reductio

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