isc-2007-hpc-in-aerodynamics-at-bmw-norbert-gruen
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BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 1
HPC in Car and Motorcycle Aerodynamics at BMW.
Outline
AerodynamicProcess
SimulationProcess
ValidationExamples
ApplicationExamples
Conclusion
EfficientDynamics
HPC in Car and MotorcycleAerodynamics at BMW.HPC in Car and MotorcycleAerodynamics at BMW.
International SupercomputerConference
June 26-29, 2007Dresden, Germany
Dr. Norbert GrünAerodynamicsSimulation
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 2
HPC in Car and Motorcycle Aerodynamics at BMW.Outline.
Aerodynamic Development.
Simulation Process.
Hardware Resources.
Various Applications.
Conclusion.
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 3
HPC in Car and Motorcycle Aerodynamics at BMW.Questions & Tools in Aerodynamic Development.
(Pre) Initial Phase Concept Phase Serial Development
Level of Detail
Tool
Question
Model
SimplifiedUnderhoodSimplified
UnderhoodIf necessary, detailsfrom predecessor
If necessary, detailsfrom predecessor
Fully detailedFully detailed
Simulation (CFD = Computational Fluid Dynamics)Simulation (CFD = Computational Fluid Dynamics)
Wind TunnelWind Tunnel
Road TestRoad Test
Integral Forces and MomentsIntegral Forces and Moments
Thermal ManagementThermal Management
Soiling, Snow DepositionSoiling, Snow Deposition
Dynamic Properties (Unsteady Aerodynamics)Dynamic Properties (Unsteady Aerodynamics)
VirtualVirtual
1:2.5 1:2.5 1:1 1:1
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 4
HPC in Car and Motorcycle Aerodynamics at BMW.CFD (Computational Fluid Dynamics) Method.
PowerFLOW™ Key Features
Lattice-Boltzmann Method (Release 3.x with 34 States, 4.x using 19 states)
Transient simulation.
Low Re-#: Direct simulation without model assumptions.
High Re-#: VLES (Very Large Eddy Simulation) in the fluid.Boundary Layer modeled by an extended log-law(accounting for local pressure gradients).
No manual meshing required: Automatic volume discretizationusing cubic cells (lattice) of different size (variable resolution).
Automatic decomposition for parallel processing.
Stable solutions.
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 5
HPC in Car and Motorcycle Aerodynamics at BMW.Simulation Process (PowerFLOW).
Geometry Group
Aerodynamics Group
SimulationPowerFLOW≈ 1 Day
SimulationPowerFLOW≈ 1 Day
PostprocessingPowerVIZ
PostprocessingPowerVIZ
ResultResult
Shape Modificationof CAD/CAS Data
Shape Modificationof CAD/CAS Data
Morphing of theSurface Mesh
(PowerCLAY)
Morphing of theSurface Mesh
(PowerCLAY)
Turnaround
2-14 Days
Turnaround
2-14 Days
CAD ModelCATIA/PRISMA
CAD ModelCATIA/PRISMA
U-Hood/U-BodyU-Hood/U-Body
CAS ModelALIAS
CAS ModelALIAS
Clay ModelPOLYWORKS
Clay ModelPOLYWORKS
Styling ExteriorStyling Exterior
Simulation Model(Surface Facetization)
ANSA, PolyWorks, PowerWRAP, ...1- 10 Days
Simulation Model(Surface Facetization)
ANSA, PolyWorks, PowerWRAP, ...1- 10 Days
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 6
HPC in Car and Motorcycle Aerodynamics at BMW.Geometry Input (Facetized Components).
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 7
HPC in Car and Motorcycle Aerodynamics at BMW.Geometry Modification by „Morphing“.
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 8
HPC in Car and Motorcycle Aerodynamics at BMW.Automatic Discretization.
Typical cell counts for external aerodynamiccases range from 20-80 milion cells.
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
Geometry representationembedded in a lattice of cubic cells (with differentlevels of resolution).
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 9
HPC in Car and Motorcycle Aerodynamics at BMW.Transient Simulation.
Time
Dra
g an
d Li
ft C
oeffi
cien
ts [-
]
Drag (Sampling Rate 13 Hz)
Lift (Sampling Rate 13 Hz)
Drag (Sampling Rate 100 Hz)
Lift (Sampling Rate 100 Hz)1 second
0.100
0.010
Drag Time Average
Lift Time Average
Simulation time steps are in the order of 10-5 to 10-4 seconds
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 10
HPC in Car and Motorcycle Aerodynamics at BMW.History of Computer Resources.
288 288
416
253
224
824 24
4896
224
0
50
100
150
200
250
300
350
400
450
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
Number of Cores
1200 full car simulations accomplished by 30 usersData production rate ≈ 20 TB/year
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 11
HPC in Car and Motorcycle Aerodynamics at BMW.History of Computer Resources.
Dedicated PowerFLOW Server
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 12
HPC in Car and Motorcycle Aerodynamics at BMW.
0,50,60,70,80,91,01,11,21,31,41,51,61,71,81,92,0
32 48 64 80 96 112 128Number of Cores
Spee
dup
Linear
PowerFLOW 3.6a
PowerFLOW 4.0a
Parallel Efficiency.
Benchmark „medium“ on HP Superdome (Montecito, 1.6GHz)
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 13
HPC in Car and Motorcycle Aerodynamics at BMW.Case Size.
0
500
1.000
1.500
2.000
2.500
3.000
3.500
2001 2002 2003 2004 2005 2006 2007
Cas
e C
ompl
exity
[GVo
TS]
The size of a case (determining the computational effort) is expressed as the product of cells (voxels) and timesteps
GVoTS = Giga Voxel Time Steps
The size of a case (determining the computational effort) is expressed as the product of cells (voxels) and timesteps
GVoTS = Giga Voxel Time Steps
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
10·106 cells x 50·103 TSSimple Models, isothermal
10·106 cells x 50·103 TSSimple Models, isothermal
20·106 cells x 50·103 TSDetailed Uhood & U-body, isothermal
20·106 cells x 50·103 TSDetailed Uhood & U-body, isothermal
30·106 cells x 100·103 TSFully detailed incl. heat transfer
30·106 cells x 100·103 TSFully detailed incl. heat transfer
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 14
HPC in Car and Motorcycle Aerodynamics at BMW.Performance Development.
The common performance measure of FLOPSdoes not help us to predict expected runtimes.
Instead we use the ratio of GVoTS / CPU-h
0,45
0,30
0,60
0,80
0,20
0,30
0,40
0,50
0,60
0,70
0,80
0,90
Jan 02 Jan 03 Jan 04 Jan 05 Jan 06 Jan 07
Cor
e Pe
rfor
man
ce in
GVo
TS/C
PU-h
SGI OriginR14000 / 0.6GHz
HP SuperdomeMadison / 1.5GHz
SGI AltixItanium 2 / 1.6GHz
HP SuperdomeMontecito / 1.6GHz
Benchmark „medium“ (21 Mio. Voxels)
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 15
HPC in Car and Motorcycle Aerodynamics at BMW.Comparison of Simulation and Experiment.
-0,100
-0,050
0,000
0,050
0,100
0,150
0,200
0,250
0,300
0,350
0,400
0,450
0,500D
rag
and
Lift
Coe
ffici
ents
Cx PowerFLOW
Cx Wind Tunnel
Cz-rear PowerFLOW
Cz-rear Windtunnel
Array of different Vehicles
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 16
HPC in Car and Motorcycle Aerodynamics at BMW.Lift Analysis.
-0,03
-0,02
-0,01
0,00
0,01
0,02
0,03
0,0 0,1 0,3 0,4 0,5 0,6 0,7 0,9 1,0
-0,40
-0,30
-0,20
-0,10
0,00
0,10
0,200,0
Cz(x) Verteilung
Cz(x) Integral
CZ1CZ2
0.011 0.0130.143 0.123
CFD (PowerFLOW)
BMW Wind Tunnel
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 17
HPC in Car and Motorcycle Aerodynamics at BMW.Flow Field Visualization.
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 18
HPC in Car and Motorcycle Aerodynamics at BMW.Passenger Comfort.
Simulation with Screen Simulation without ScreenDraft Test Dummies in the Wind Tunnel
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
Transient IsosurfaceVx=0 (Reverse Flow)
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 19
HPC in Car and Motorcycle Aerodynamics at BMW.Temperature Loads (from Oil Cooler and Exhaust).
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 20
HPC in Car and Motorcycle Aerodynamics at BMW.Exhaust Gas Propagation.
X5old
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
Isosurfaces of Exhaust Gas with T=50°C Time averaged Flow Field
X5new
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 21
HPC in Car and Motorcycle Aerodynamics at BMW.Detail Optimization.
Wing MirrorSub-Simulation Volume
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
Reduced Effort due toSub-Simulations aroundDetails like Wing Mirrors,Wheelhouse, etc.
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 22
HPC in Car and Motorcycle Aerodynamics at BMW.Aerodynamic Forces on Parts.
Magnitude, Direction and Point of Incidence
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 23
HPC in Car and Motorcycle Aerodynamics at BMW.Aerodynamic Forces on Parts.
TouringTouring StandardStandard
SportSport
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion StandardStandard
Forces on the Driver‘s Helmetwith different Windshields.
HelmkraftSportSportTouringTouring
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 24
HPC in Car and Motorcycle Aerodynamics at BMW.Aerodynamics and Stability.Simulation of Gusty Environments.
Gust simulated via time dependent cross flow velocitytravelling downstream over the car.
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 25
HPC in Car and Motorcycle Aerodynamics at BMW.Aerodynamics and Stability.Gust Response of different Vehicles.
-0,04
-0,02
0,00
0,02
0,04
0,06
0,08
0,10
1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5Time [s]
Yaw
ing
Mom
ent C
oeffi
cien
t
Car ACar B
CMZ >0
CMZ <0
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 26
HPC in Car and Motorcycle Aerodynamics at BMW.Wind Tunnel Design.
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
BMW GroupDr. Norbert Grün
InternationalSupercomputerConference
June 26-29, 2007Dresden, Germany
Page 27
HPC in Car and Motorcycle Aerodynamics at BMW.Conclusion.
ADVANTAGES
+ Significant progress has been made in the past five yearsand the field of application has broadened.
+ The level of detail that can be handled and the achievable accuracypermit productive usage as a complementary tool to the wind tunnel.
+ Usage does not require a numerics expert, CFD can be employed by the aerodynamicist.
SHORTCOMINGS
- Detail optimization loops with CFD still slower than the wind tunnel.
Outline
AerodynamicDevelopment
SimulationProcess
HardwareResources
VariousApplication
Conclusion
- Computer hardware requirements are very high for competitive processtimes, although the per-processor performance has more than doubled in the past five years.
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