ISC-2007-HPC-in-Aerodynamics-at-BMW-Norbert-Gruen

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


Dr. Norbert GrünAerodynamicsSimulation




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




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


SimulationProcess

HardwareResources

VariousApplication

Conclusion




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


SimulationProcess

HardwareResources

VariousApplication

Conclusion




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


SimulationProcess

HardwareResources

VariousApplication

Conclusion




Page 6

HPC in Car and Motorcycle Aerodynamics at BMW.Geometry Input (Facetized Components).

Outline


SimulationProcess

HardwareResources

VariousApplication

Conclusion




Page 7

HPC in Car and Motorcycle Aerodynamics at BMW.Geometry Modification by „Morphing“.

Outline


SimulationProcess

HardwareResources

VariousApplication

Conclusion




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


SimulationProcess

HardwareResources

VariousApplication

Conclusion

Geometry representationembedded in a lattice of cubic cells (with differentlevels of resolution).




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


SimulationProcess

HardwareResources

VariousApplication

Conclusion




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


SimulationProcess

HardwareResources

VariousApplication

Conclusion




Page 11

HPC in Car and Motorcycle Aerodynamics at BMW.History of Computer Resources.

Dedicated PowerFLOW Server

Outline


SimulationProcess

HardwareResources

VariousApplication

Conclusion




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


SimulationProcess

HardwareResources

VariousApplication

Conclusion




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


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




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


SimulationProcess

HardwareResources

VariousApplication

Conclusion




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


SimulationProcess

HardwareResources

VariousApplication

Conclusion




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


SimulationProcess

HardwareResources

VariousApplication

Conclusion




Page 17

HPC in Car and Motorcycle Aerodynamics at BMW.Flow Field Visualization.

Outline


SimulationProcess

HardwareResources

VariousApplication

Conclusion




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


SimulationProcess

HardwareResources

VariousApplication

Conclusion

Transient IsosurfaceVx=0 (Reverse Flow)




Page 19

HPC in Car and Motorcycle Aerodynamics at BMW.Temperature Loads (from Oil Cooler and Exhaust).

Outline


SimulationProcess

HardwareResources

VariousApplication

Conclusion




Page 20

HPC in Car and Motorcycle Aerodynamics at BMW.Exhaust Gas Propagation.

X5old

Outline


SimulationProcess

HardwareResources

VariousApplication

Conclusion

Isosurfaces of Exhaust Gas with T=50°C Time averaged Flow Field

X5new




Page 21

HPC in Car and Motorcycle Aerodynamics at BMW.Detail Optimization.

Wing MirrorSub-Simulation Volume

Outline


SimulationProcess

HardwareResources

VariousApplication

Conclusion

Reduced Effort due toSub-Simulations aroundDetails like Wing Mirrors,Wheelhouse, etc.




Page 22

HPC in Car and Motorcycle Aerodynamics at BMW.Aerodynamic Forces on Parts.

Magnitude, Direction and Point of Incidence

Outline


SimulationProcess

HardwareResources

VariousApplication

Conclusion




Page 23

HPC in Car and Motorcycle Aerodynamics at BMW.Aerodynamic Forces on Parts.

TouringTouring StandardStandard

SportSport

Outline


SimulationProcess

HardwareResources

VariousApplication

Conclusion StandardStandard

Forces on the Driver‘s Helmetwith different Windshields.

HelmkraftSportSportTouringTouring




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


SimulationProcess

HardwareResources

VariousApplication

Conclusion




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


SimulationProcess

HardwareResources

VariousApplication

Conclusion




Page 26

HPC in Car and Motorcycle Aerodynamics at BMW.Wind Tunnel Design.

Outline


SimulationProcess

HardwareResources

VariousApplication

Conclusion




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


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.

HPC in Car and MotorcycleAerodynamics at BMW.

Thank You for Your Attention.

EfficientDynamics

International SupercomputerConference


Dr. Norbert GrünAerodynamicsSimulation

ISC-2007-HPC-in-Aerodynamics-at-BMW-Norbert-Gruen

Documents

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