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CTH2008w07TW, Aerodynamics, Tim Walker
Page 1Issue date: 2008-02-15, Security Class: Public
Aerodynamics at Volvo Car CorporationKTH 2008
Tim Walker and Simone SebbenVolvo Car Corporation
CTH2008w07TW, Aerodynamics, Tim Walker
Page 2Issue date: 2008-02-15, Security Class: Public
Overview
• Organisation• Influence of Aerodynamics on Passenger Cars
• Why is aerodynamics important• Development• Facilities
• Test Techniques• Moving Ground
CTH2008w07TW, Aerodynamics, Tim Walker
Page 3Issue date: 2008-02-15, Security Class: Public
VCC Environmental & Fluid Dynamics Centre
•Research and Development
•Complete vehicle Engineering
•Environment and Fluid Dynamics
Thermodynamics Dirt & WaterManagement CFD Fuel Economy Recicle of
Materiasl WeightAerodynamics
CTH2008w07TW, Aerodynamics, Tim Walker
Page 4Issue date: 2008-02-15, Security Class: Public
VCC Environmental & Fluid Dynamics Centre
Thermodynamics Aerodynamics CFD Dirt & Water.
Cooling Performance Thermal Environment: Engine bay Floor Air Intake / Intercooler 13 People: 3 Mechanics 2 B.Sc. 7 M.Sc. 1 Lic.
Drag Stability 11 People: 1 Mechanics 7 M.Sc. 1 Lic. 1 Ph.D
Aerodynamics Climatic Comfort Thermodynamics Aeroacustics Water/Dirt Manag. 15 People: 5 M.Sc. 2 Lic. 8 Ph.D
Dirt Deposition Water Tightness 13 People: 5 B.Sc. 7 M.Sc. 1 Lic.
Requirement specification, Customer requirements, Project management Testing / System simulations, R&D / method development
•Plus 1 Aerodynamicist resident at the Design Studio
CTH2008w07TW, Aerodynamics, Tim Walker
Page 5Issue date: 2008-02-15, Security Class: Public
• Drag (fuel consumption, top speed, acceleration)
• High-speed stability (lift)
• Cross-wind stability (side force and yawing moment)
• Passenger comfort (cabriolets)
• Dirt deposition (visibility)
• Aero acoustics (limiting the strength of sources)
• Body deformation (Door frames etc)
Influence of Aerodynamics
CTH2008w07TW, Aerodynamics, Tim Walker
Page 6Issue date: 2008-02-15, Security Class: Public
Calculated effect of changed CDxA on fuelconsumption and performance
Rule of thumb:A 10% reduction of CdxA will reduce the NEDC fuel consumption by 3%
CTH2008w07TW, Aerodynamics, Tim Walker
Page 7Issue date: 2008-02-15, Security Class: Public
CTH2008w07TW, Aerodynamics, Tim Walker
Page 8Issue date: 2008-02-15, Security Class: Public
CTH2008w07TW, Aerodynamics, Tim Walker
Page 9Issue date: 2008-02-15, Security Class: Public
Challenges facing Aerodynamicists
• Styling• Manufacturing
• Parts• Assembly
• Packaging• Visibility• Other attributes (eg Thermo, dirt, handling ……)• ”Carry-over” content• Cost!!!
CTH2008w07TW, Aerodynamics, Tim Walker
Page 10Issue date: 2008-02-15, Security Class: Public
Aerodynamics through the ages
Cd v Year
0,25
0,30
0,35
0,40
0,45
0,50
0,55
0,60
1950 1960 1970 1980 1990 2000 2010 20200,361995V40
0,341995S40
0,381985480ES
0,391986460
0,342003S40N
0,352004V50
0,402002XC90
0,332000V70
0,311998S80
0,341993855
0,351992854
0,401990960
0,401985765
0,441982760
0,421979343
0,451975245
0,471974240
0,611968P1800ES
0,481963P1800
0,481960Amazon
0,501955PV 544
CdYear
CTH2008w07TW, Aerodynamics, Tim Walker
Page 11Issue date: 2008-02-15, Security Class: Public
Aerodynamics through the ages
0,361995V40
0,341995S40
0,381985480ES
0,391986460
0,342003S40N
0,352004V50
0,402002XC90
0,332000V70
0,311998S80
0,341993855
0,351992854
0,401990960
0,401985765
0,441982760
0,421979343
0,451975245
0,471974240
0,611968P1800ES
0,481963P1800
0,481960Amazon
0,501955PV 544
CdYear
CdxA v Year
0,60
0,70
0,80
0,90
1,00
1,10
1,20
1950 1960 1970 1980 1990 2000 2010 2020
CTH2008w07TW, Aerodynamics, Tim Walker
Page 12Issue date: 2008-02-15, Security Class: Public
Aerodynamics through the ages
0,361995V40
0,341995S40
0,381985480ES
0,391986460
0,342003S40N
0,352004V50
0,402002XC90
0,332000V70
0,311998S80
0,341993855
0,351992854
0,401990960
0,401985765
0,441982760
0,421979343
0,451975245
0,471974240
0,611968P1800ES
0,481963P1800
0,481960Amazon
0,501955PV 544
CdYear
Frontal Area v Year
1,50
1,70
1,90
2,10
2,30
2,50
2,70
2,90
1950 1970 1990 2010
CTH2008w07TW, Aerodynamics, Tim Walker
Page 13Issue date: 2008-02-15, Security Class: Public
Development process
Concept studyConcept study
• Generic shape studies• Evaluate styling proposals• Define underfloor concepts
•Analysis and research of previous models and competitors•Simple scale model tests (parameter studies)•Semi-detailed CFD (parameter studies)•Create guidelines to design and engineering•Create aerodynamic ”hard points”
CTH2008w07TW, Aerodynamics, Tim Walker
Page 14Issue date: 2008-02-15, Security Class: Public
Development process
PrestudyPrestudy
• Develop frozen design• Develop underfloor solutions
•Analyse and suggest improvements to many designs (CFD and models)•Give recommendations when choosing design•Develop and improve chosen design using full-scale clay model and fullydetailed CFD modelling•Confirm and approve the chosen design’s predicted characteristics
CTH2008w07TW, Aerodynamics, Tim Walker
Page 15Issue date: 2008-02-15, Security Class: Public
Development process
ProjectProject
• Detail optimization• Verification
•Fine tuning of pre-production prototypes•Confirm and approve all characteristics•Follow up any late design changes•Confirm production car
CTH2008w07TW, Aerodynamics, Tim Walker
Page 16Issue date: 2008-02-15, Security Class: Public
Concept studyConcept study
• Generic shape studies• Evaluate styling proposals• Define underfloor concepts
PrestudyPrestudy
• Develop frozen design• Develop underfloor solutions
ProjectProject
• Detail optimization• Verification
36-48 months
CTH2008w07TW, Aerodynamics, Tim Walker
Page 17Issue date: 2008-02-15, Security Class: Public
In-house testing in three wind tunnels, Gothenburg
PVT MWT Climatic Test section 27m2 (6.6mx4.1m , length 15.8m) Max speed 250 kph Temp. +20 to 60° C Chassi dyn. load 150 kW Sun sim. max 1200 W/m2
1:5 scale of PVT Test section 1.1m2
Max. speed 200 kph
Test section/nozzle 11.2m2 Max. speed 200 kph Temp range -40 to +50° C Chassi dyn. load 280 kW Sun sim. max 1200 W/m2
Wind tunnel facilities at Volvo
CTH2008w07TW, Aerodynamics, Tim Walker
Page 18Issue date: 2008-02-15, Security Class: Public
Full-scale wind tunnel (PVT)Test capabilities:
Aerodynamics
Hot Climate/Thermo
Soiling
Wind Noise
CTH2008w07TW, Aerodynamics, Tim Walker
Page 19Issue date: 2008-02-15, Security Class: Public
Road testing (soiling, snow deposition)
• Dirt deposition tests in Sweden and USA
• Snow deposition in Jokkmokk
Road Testing
CTH2008w07TW, Aerodynamics, Tim Walker
Page 20Issue date: 2008-02-15, Security Class: Public
Dirt deposition testing in the Volvo wind tunnel
• Detection of emitted light from an UV sensitive chemical dissolved in water
• The signal from a set of UV sensitive cameras are recorded by a frame grabber card in a PC
• Image processing is used to evaluate the dirt deposition
CTH2008w07TW, Aerodynamics, Tim Walker
Page 21Issue date: 2008-02-15, Security Class: Public
Side window dirt deposition
Video snapshot
Picture of the dirt deposition build up
Separation of fine spray from droplets
Quantification of dirt deposition build up
Image processing sequence
CTH2008w07TW, Aerodynamics, Tim Walker
Page 22Issue date: 2008-02-15, Security Class: Public
Std 2001 Mirror 2003 Mirror
CTH2008w07TW, Aerodynamics, Tim Walker
Page 23Issue date: 2008-02-15, Security Class: Public
Physical Test objects
• Clay model (1:5 or 1:1 scale)
• Plastic model
• Mock-up (metal/plastic exterior)
• Prototype
• Production vehicle
CTH2008w07TW, Aerodynamics, Tim Walker
Page 24Issue date: 2008-02-15, Security Class: Public
• Balance measurements
– Effect of configuration changes on aero coefficients
– Investigate sensitivity to flow angle, vehicle attitude and wind speed
Conventional aerodynamic testing
CTH2008w07TW, Aerodynamics, Tim Walker
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•Pressure measurements
•Flow visualization (smoke, surface paint, tufts)
Conventional aerodynamic testing
CTH2008w07TW, Aerodynamics, Tim Walker
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•Pressure Measurements
•Base pressure measurements
• Wake analysis (seven-hole pressure probe measurements)
• Image processing methods applied to soiling
Methods to increase the knowledge gained from aerodynamic testing
CTH2008w07TW, Aerodynamics, Tim Walker
Page 27Issue date: 2008-02-15, Security Class: Public
Wake measurements
dydzUPUPD )( 222
211 ρρ −−+= ��
Seven-hole probe rake
Floor traverse
CTH2008w07TW, Aerodynamics, Tim Walker
Page 28Issue date: 2008-02-15, Security Class: Public
Wake analysis
Total pressure Microdrag
Wake measured 100 mm downstream of a notchback
Identify regions that can be improved
CTH2008w07TW, Aerodynamics, Tim Walker
Page 29Issue date: 2008-02-15, Security Class: Public
Sources of drag on a modern car
45%
30%
25%
CTH2008w07TW, Aerodynamics, Tim Walker
Page 30Issue date: 2008-02-15, Security Class: Public
Why Moving Ground is Neccessary
Provides correct relative movement between the car body and tunnel floor
Provides correct relative movement between the car body and wheels
Correct simulation of the flow influences:•Under body optimisation•Upper body optimisation
Influences flow under and around car
CTH2008w07TW, Aerodynamics, Tim Walker
Page 31Issue date: 2008-02-15, Security Class: Public
How: Stationary Floor and Wheels
Wind
CTH2008w07TW, Aerodynamics, Tim Walker
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How: Moving Ground and Rotating Wheels
Wind
Road/Floor
CTH2008w07TW, Aerodynamics, Tim Walker
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Optimisation affectedRoof and boot
Front-end and deflectors
Underbody design
Wheel Design
CTH2008w07TW, Aerodynamics, Tim Walker
Page 34Issue date: 2008-02-15, Security Class: Public
Wind Tunnel Uppgrade
•Installation of 5-belt moving ground
•Steel belts
•Improved Boundary Layer control
•Wind speed increased to 250km/h
•Work started July 2005
•Work completed January 2007
Volvo Full Scale Moving Ground
CTH2008w07TW, Aerodynamics, Tim Walker
Page 35Issue date: 2008-02-15, Security Class: Public
Centre belt
Wheel Drive Units
Supporting struts
5 belt concept
Volvo Full Scale Moving Ground
CTH2008w07TW, Aerodynamics, Tim Walker
Page 36Issue date: 2008-02-15, Security Class: Public
Measuring Frame for WDU’s and struts
Volvo Full Scale Moving Ground
CTH2008w07TW, Aerodynamics, Tim Walker
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Moving Ground Installation
CTH2008w07TW, Aerodynamics, Tim Walker
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Moving Ground Installation
CTH2008w07TW, Aerodynamics, Tim Walker
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Moving Ground F1 Installation
CTH2008w07TW, Aerodynamics, Tim Walker
Page 40Issue date: 2008-02-15, Security Class: Public
Aero Concept Car
CTH2008w07TW, Aerodynamics, Tim Walker
Page 41Issue date: 2008-02-15, Security Class: Public
Volvo 3C Concept Car 2004
Cd=0.20