Fluent Ug m 2005
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Transcript of Fluent Ug m 2005
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8/13/2019 Fluent Ug m 2005
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03/02-03/2006 Robert Bosch GmbH reserves all rights even in the event of industrial property rights.
We reserve all rights of disposal such as copying and passing on to third parties.
1
Fluent CFD Summit 2005
Computational Aero-Acoustics
3D Computational Aero-Acoustics
Simulation of Air Intake-Induced Whistles
Venkatesh Kannan4 Core Development, Robert Bosch Corporation, Farmington Hills, MI
Sandeep D. Sovani, Ph.D4 Fluent Inc, Ann Arbor, MI
Dave S. Greeley, Ph.D4
Air Flow Research, Robert Bosch Corporation, Waltham, MA
Ashok Khondge4 Fluent Pvt. Ltd., Pune, India
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Fluent CFD Summit 2005
Computational Aero-Acoustics
Abstract
4 Introduction
4 Background
4 3D Computational Simulations
4 Correlation
4 Lessons Learnt
4 Conclusions
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Fluent CFD Summit 2005
Computational Aero-Acoustics
A distinct whistle at
4 2900 - 3400 Engine RPM
4 72 - 78% Engine Load
4 35-45 Throttle Angle
Hemi-anechoic - Chassis Dyno
Test Data
Introduction
2200Hz
88.4dB
SPL,
dB
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4
Fluent CFD Summit 2005
Computational Aero-Acoustics
Modified Geometry
Ramp (16) & Radius (2 mm)
Baseline Geometry
Cavity
Design Solution
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5
Fluent CFD Summit 2005
Computational Aero-Acoustics
Baseline
110
100
90
80
70
60
50
SPL,
dB
Modified
Airflow
=43
Baseline
=43
Airflow
Modified
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6
Fluent CFD Summit 2005
Computational Aero-Acoustics
4 Detailed sensitivity studies
conducted experimentally4 Presented at Fluent UGM
2004
4 Presented at SAE 2004
WorldCongress, Detroit, MIPaper # 2004-01-0395
4 Do provide a design solution but
do not provide insight into the
whistle physics
4 Experiments are expensive
Need for Simulation
__Disturb Flowat A & B
B
__Disturb Flow at A
A
Airflow
__Eliminate Cavity C
C
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Fluent CFD Summit 2005
Computational Aero-Acoustics
4 CFD-CAA simulations conducted for physical insight
4 2D simulations conducted first
4 Can replicate whistle
4 But frequency under-predicted
4 Difference in whistle magnitude between baselineand modified designs not predicted well
4 Presented results at Fluent UGM2004
4 Also presented at SAE NVH Conference, TraverseCity, MI, Paper # 2005-01-2364
Background
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Fluent CFD Summit 2005
Computational Aero-Acoustics
434 18000 2D Quad Cells,4 k- RNG Turbulent Model
4 Unsteady Simulation
4 Coupled Solver
4 2nd Order Upwind
4 Time Step = 2.5e-05s
4 Run Time = 0.04s
4 Ideal Gas Law
4 Double Precision Solver
High Mesh
Density
Inlet
(101325 Pa)Throttle
PlateSump
Zip TubeOutlet
92325Pa
P = 9kPa
2D Computational Simulation
Monitor
Point A
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Fluent CFD Summit 2005
Computational Aero-Acoustics
80
100
120
140
160
180
0 1000 2000 3000 4000 5000Frequency (Hz)
SPL
(dB) Design A
152 dB @ 1710 Hz
Experimental - 3D Computational - 2D
159dB @
2125Hz
152dB @
1710Hz
Correlation - Sound Pressure Level at Point A
4 Baseline Geometry
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10
Fluent CFD Summit 2005
Computational Aero-Acoustics
80
100
120
140
160
180
0 1000 2000 3000 4000 5000
Frequency (Hz)
SPL
(dB)
137dB @
2125Hz
Experimental - 3D Computational - 2D
149dB @
1800Hz
Correlation - Sound Pressure Level at Point A
4 Modified Geometry
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We reserve all rights of disposal such as copying and passing on to third parties.
12
Fluent CFD Summit 2005
Computational Aero-Acoustics
4 4221265 cells ( Hex+tet, Hex dominant),
4 LES with Smagorinsky-Lilly subgrid
model (Dynamic Model)
4 Unsteady Simulation
4 Segregated Solver
4 Discretizations
4 2nd order upwind for pressure,density and energy
4 Bounded Central Differencing
for momentum
4 Time Step = 2.5e-05 sec
4 Total Run Time = 0.03775 sec
4 Ideal Gas Law
4 Double Precision Solver
3D Computational Simulation
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13
Fluent CFD Summit 2005
Computational Aero-Acoustics
Simulated Flow Structure4 Contours of velocity magnitude on central vertical plane
2D 3D
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14
Fluent CFD Summit 2005
Computational Aero-Acoustics
Simulated Flow Structure4 Contours of static pressure on central vertical plane
2D 3D
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15
Fluent CFD Summit 2005
Computational Aero-Acoustics
80
100
120
140
160
180
0 1000 2000 3000 4000 5000
Frequency (Hz)
SPL(d
B)
Design A
152 dB @ 1710 Hz
Experimental - 3D Computational - 2D
159dB @
2125Hz
152dB @
1710Hz
Correlation - Sound Pressure Level at Point A
4 Baseline Geometry
Computational - 3D
157.8dB @
2098Hz
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We reserve all rights of disposal such as copying and passing on to third parties.
16
Fluent CFD Summit 2005
Computational Aero-Acoustics
80
100
120
140
160
180
0 1000 2000 3000 4000 5000
Frequency (Hz)
SPL(dB)
137dB @
2125Hz
Experimental - 3D Computational - 2D
149dB @
1800Hz
Correlation - Sound Pressure Level at Point A
4 Modified Geometry
Computational - 3D
152.6dB
@ 2098Hz
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17
Fluent CFD Summit 2005
Computational Aero-Acoustics
Conclusions
4 Baseline geometry 3D simulations
4 Very accurate compared to experiments
4 Whistle frequency as well as magnitude predicted properly
4 Modified geometry 3D simulations
4 Whistle frequency predicted very accurately, but amplitude is off
4 Causes are under investigation
4 It is possible that CFD model differs slightly from actual geometry
4 3D computational simulation (although computation intensive) provide
additional insights better accuracy as compared with experiments than
2D simulations
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18
Fluent CFD Summit 2005
Computational Aero-Acoustics
Long Term Goals
Benefits
4 Understanding of the influence of small geometric details on
the mechanism of whistle production and suppression
4 Novel ideas for the flow path geometry features that can
effectively suppress or produce the aero-acoustic sources
Conclusions
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19
Fluent CFD Summit 2005
Computational Aero-Acoustics
Acknowledgements
4 Dave Hanner
4John RydzewskiGeneral Motors Corporation
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Fluent CFD Summit 2005
Computational Aero-Acoustics
Questions & Answers