1 eMarking: staff and student perceptions Liz Burd, Durham University.
Computational Aero-Acoustics - Siemens David Burd, FFTNA. 2 Copyright Free Field Technologies...
Transcript of Computational Aero-Acoustics - Siemens David Burd, FFTNA. 2 Copyright Free Field Technologies...
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Computational Aero-Acoustics
STAR-CCM+ / ACTRAN for Computational Aero-Acoustics
CD-adapco STAR AMERICAS Conference, June 28, 2011
Authors: Yves Detandt, Marie Cabrol, Romain Leneveu, Diego D’Udekem, FFT
Fred Mendonca, CD-adapco
Presenter: David Burd, FFTNA
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Contents
Introduction - Hybrid Acoustic Approach
Tandem Cylinder Benchmark
Tandem Cylinders Problem Statement
CFD input
ACTRAN simulation
Results
Automotive HVAC Noise Example
Fan Noise Example
Conclusions
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Introduction - Hybrid Acoustic Approach
1. Unsteady flow computation (STAR-CCM+)
2. Acoustic noise sources computation and propagation (ACTRAN)
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Tandem cylinder benchmark
The First Workshop on Benchmark problems for Airframe Noise
Computations (BANC-I) was held in Stockholm, Sweden, June 10-11,
2010. The workshop was organized by the Discussion Group on
Benchmark Experiments and Computations for Airframe Noise
(BECAN),1 which is jointly sponsored by the Fluid Dynamics and
Aeroacoustics Technical Committees of AIAA.
The BANC Tandem Cylinders model is available here:
https://info.aiaa.org/tac/ASG/FDTC/DG/BECAN_files_/Workshop_June_
2010_Final_Problem_Statements
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Problem Statement
Flow Speed:
Mach 0.128
U0 = 44 m/s 158 km/h
Re = 1.66 x 105
Experimental Configuration:
12D span for flow measurements (BART)
16D span for acoustic measurements (QFF)
Experimental configuration (ref 2.)
Tandem Cylinders - Geometry (ref 1.)
Schematic of microphone locations (ref 2.)
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CFD Input
CFD1 (Provided by Fred Mendonca, CD-adapco, on STAR-CCM+ v5.06.007)
Grid: 6.7 million cells
Dimensions of the computational domain:
• 33.7D x 30D x 12D
Time step: 10-5 s
Time interval for spectral analysis:
• 0.46503 s to 0.56503 s (0.1 s)
Data size: 1.2 TB (mesh+solution)
Boundary conditions :
• Free Stream: M = 0.128
• No-slip at cylinder walls
• Periodic boundary conditions in the spanwise direction
Aeroacoustic results limited to 2800 Hz
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CFD Input
CFD2: reduced CFD domain + coarser mesh (STAR-CCM+ v5.06.007)
Grid: 1.07 million cells
Dimensions of the computational domain: 24D x 11D x 12D
Time step: 3.10-5 s
Time interval for spectral analysis:
• 0.27228 s to 0.37227 s (0.1 s)
Data size: 180 GB (mesh + solution)
Boundary conditions:
• Free Stream: M = 0.128
• No-slip at cylinder walls
• Periodic boundary conditions in the spanwise direction
Aeroacoustic results limited to 1000 Hz
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ACTRAN Simulations
Two different meshes/simulations were used:
CAA 1
Domain extension: 43D x 15D x 8D
159,898 dofs
Performance: 5 min/freq
Mesh valid up to 1000 Hz
CAA 2
Domain extension: 43D x 15D x 8D
1,684,270 dofs
Performance: 1.75 h/freq
Mesh valid up to 2800 Hz
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ACTRAN Simulations
Experimental coherence
Correlations reach 0 for Span/D > 8D
Simulations
Consider spans of up to 8D from CFD results
Use the symmetry of the problem
Reproduced from
AIAA-2007-3450
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Results – Microphone A
Microphone A
CFL3D results (AIAA-2007-3450)
60.10e6 CFD cells
CFD 1: 7.10e6 CFD cells
CFD 2: 10e6 CFD cells
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Results – Microphone B
Microphone B
CFL3D results (AIAA-2007-3450)
60.10e6 CFD cells
CFD 1: 7.10e6 CFD cells
CFD 2: 10e6 CFD cells
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Results – Microphone C
Microphone C
CFL3D results (AIAA-2007-3450)
60.10e6 CFD cells
CFD 1: 7.10e6 CFD cells
CFD 2: 10e6 CFD cells
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Results – Varying Data Sample Rates
Investigations on data sample rates (on CFD 1 data)
1e-5 s is the CFD time step for CFD 1
Conclusions:
Results are not sensitive to data sample rate
Data storage could be reduced by a factor of 10
This investigation is required on each test case
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Results
Correlation between different time series
Investigate the acoustic signals due to different time series in a single
ACTRAN run:
Maximum and minimum for each frequency defines the envelope
Average of 6 acoustic signals
Similar to experimental processing
t t+0.02
t+0.01 t+0.03
t+0.04
t+0.05
t+0.06
t+0.07
t+0.08
t+0.09
t+0.10
CFD results
Loadcase 1
Loadcase 2
Loadcase 3
Loadcase 4
Loadcase 5
Loadcase 6
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Automotive HVAC Noise Example
German Automotive consortium proposed a benchmark to simulate the
noise generated in a simplified HVAC configuration
Experimental setup
(reproduced from AIAA-2008-2902)
ACTRAN model (AIAA-2009-3352)
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Automotive HVAC Noise Example
Experiment:
Full anechoic wind tunnel
17 microphone array rotated
through 17 positions
Simulation:
STAR-CD: 2.5 million cells, 0.1s flow solution
ACTRAN:
Envelope of the experimental data
Differences in peak amplitudes are related to
approximations in damping modeling
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Fan Noise Example
Simplified radial compressor (12 blades)
Speed: 2000 rpm
Blade Pass Frequency: 400Hz
ACTRAN Results:
Tonal components (BPF and harmonics) due to interaction of blade unsteady load
with diffuser
Broadband level due to downstream turbulence
BPF
1st harmonic
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Tandem Cylinder Study Conclusions
Several CFD parameters were compared:
Data sampling frequency
Maximum frequency estimates from turbulent kinetic energy
Different time series
Several acoustic configurations (hard wall and duct modes variables had a
significant effect on results)
STAR-CCM+ / ACTRAN software combination provides good
correlation with experimental results.
Advantages:
No need to refine CFD grid to propagate acoustics up to an FWH surface
because Actran does not use FWH for this type of analysis.
Several acoustic investigations can be performed using the same CFD data.
Acoustic boundary conditions (free field, duct modes, etc.) were imposed
separately from CFD boundary conditions.
Actran includes convenient acoustic post processing.