Modelling and Simulation in Aeroacoustics Current Practice and Future Challenges

Fred Mendonça

HVAC, ECS, Duct ventilation and discharge

AIAA2012-2068

External Aeroacoustic Excitation and

Internal Noise Transmission

Surface FFT (dB) at 500Hz (top)

and 1000Hz (bottom)

AIAA2012-2205

AIAA2012-2206

SAE2013-01-0640

Airframe and Jet noise

Turbo compressor Noise

GT2012-70028

HVAC – blower, distributor, ducts

SAE13-01-0856

Pipe singing

AIAA2012-2171

Sunroof/side-window buffeting – real vehicle effects

Uncorrected

Correlated

Aluminium

Perspex MDF

– Wall compliance effects

• Full FSI of compliant walls (below left)

• Correlations for wall compliance (below right)

– Leakages

SAE2013-01-1012

Hydroacoustics / cavitation noise

– Sound propagation in compressible liquid media

– Sound wave absorption treatments to avoid boundary reflections

– Multi-phase phenomena

Aeroacoustics in v8 towards infinite possibilities

Aeroacoustics Simulations Options

Steady state Transient

Broadband

Correlations

Synthesized

Fluctuations SNGR

CURLE surface

PROUDMAN volume

GOLDSTEIN 2D-axi

LEE

Lilley

Mesh Frequency Cut-off

LES

DES

Transient RANS

Point/Surface FFTs and iFFTs

Auto and Cross Spectra – coherence and phase

FW-H

Export commercial propagation codes

Export to

Propagation codes

Direct Noise Propagation

1D (and 2D) Wavenumber analysis

Focus on Transient and Aeroacoustics

– LES-type turbulence model • DES (options of Spalart-Allmaras, k-ε, k-ωSST)

• DES advection scheme blending

• Full LES (wall resolved or under-resolved ! )

– Advanced wall treatment • y+ insensitive

– Non-reflecting conditions for • Inflow and outflow boundaries

– Full Compressibility • Interaction between the flow and acoustics

– Especially for cavity resonance

– Very efficient commercial transient solver • 2nd order space and time discretisation

– Spectral Analysis • FFT and iFFTs at points and surfaces

• Auto and Cross spectra – coherence and phase

• Frequency and Wave Number Fourier analysis

FFT post-processing (point)

– Monitor point in mirror wake

– Tail-off in predicted spectrum at mesh cut-off frequency of ~1000 Hz

STAR

Experiment

Direct Propagation in STAR-CCM+

– Mesh requirement

• 20 cells per acoustic wavelength ( λ= c / f )

– In ambient conditions, you need cells of ~15mm to propagate a signal at 1000Hz

–Domain size = 1000D, (~10 λ )

–Double precision code

– Ideal-gas Non-reflective in/outflow boundaries

– STAR results capture the acoustic sources for propagation via

• Ffowcs Williams-Hawkings (far-field propagation of compact sources without internal reflections)

– STAR offers coupling to 3rd party propagation codes:

• FFT, ACTRAN

• LMS, Virtual.Lab.Acoustics

• ESI, VA-One

– VibroAcoustics

• Using FVS in STAR-CCM+

• Export to SEA and FEA

100 Hz 500 Hz

3150 Hz Overall

Propagation – FW-H and 3rd party code export

Introduction to 1D (line) WaveNumber Analysis

Φc(k,ѡ)

ѡ

k

k0=ѡ/c0

kc=ѡ/Uc

Φ0 (k, ѡ)

Φc(k,ѡ)

ѡ

k

k0=ѡ/c0

kc=ѡ/Uc

Φ0 (k, ѡ)

Bremner and Wilby AIAA-2002-2551

Wavenumber (rad/m)

Idealised side-view mirror

DARP acoustic tunnel open section

40ms-1 open jet

Mirror height is 15cm

Re = 2x105 based on mirror diameter (half dimensions of the original

Daimler experiment AIAA-1999-1895)

11 million cells

Refined wake and “side-glass”

2mm resolution

CFD previously validated

– AIAA-2011-2843

Southampton University Setup

1D wave number analysis on attached and separated

zones

a+ a-

u-

a+ a-

u+

2D wave number analysis at discrete frequencies

Convective ridge Acoustic circle

Separating the acoustic content

Total and acoustic power input to vibration analysis

Widely applicable modelling for flow noise prediction

Substantial investment towards

– answering current and needs

– driving future expectations

in Aeroacoustics

and

AeroVibroacoustics

THANK YOU for your KIND ATTENTION

QUESTIONS?

Summary