WS12 Aerodynamic Performance
Research Findings
21st February
2012
Mike Dickison
LCVTP Programme Manager
Coventry University
Workstream Task Summary
LCVTP WS12 Aerodynamics: Overview Project Plan
WS Summary Report
Task 1
Technology benchmark
Concept selection
Task 2
Concept evaluation study
Task 3
Conceptual packging study
Task 4
Concept vehicle
Aero performance integration
Task 5
Aero simulaton & testing
Task 6
Implementation & evaluation
Individual test reports exist
Project Resource
Five partners
•
•
•
•
•
Jaguar / LandRover (JLR)
Tata Motors European Technology Centre (TMETC)
MIRA Ltd
Ricardo
Coventry University (Workstream Leader)
Specialist input from 3 Universities
•
•
•
Cranfield
Durham
Loughborough
Task 12.1 – Technology Benchmark
Study/ Concept Selection (MIRA Lead)
• Identified technologies that are likely
to produce significant drag reduction
• The research groups from Coventry
University and MIRA searched
available literature for suitable
solutions
• Library of relevant references was
created
• Summary of all relevant data compiled
into report – see example to right
Task 12.2 – Concept Evaluation
Study (CU Lead)
Weight
Front End
Rear End
Misc.
Cooling
Underbody
Wheels /
Wheel Arches
Turning vanes
Vortex Generators
Lower bumper contraction
Air curtains
Base pressure recovery
Tapering
Cavities
Vortex generators
Wake splitting
Diffusing spoiler
Base bleed
Suction
Active spoilers
Spoilers
Synthetic jets
Rear view cameras
Surface treatment (rough/smooth)
Wind average drag
Interaction of systems
Number of radiators and placement/duct design
Direct air cooling in engine compartment
Drive cycle and thermal analysis
Radiator sizing & new materials - novel heat exchangers
Active intake blanking (radiator)
EV cooling requirements (changes depending on time)
Active intake blanking (EV specific systems)
Active intake blanking (brakes)
Synthetic jets
Vortex generators
Surface treatment of flat underbodies (rough/smooth)
Underbody Diffusers (Front and Rear)
Shaped wheel deflectors
Wheel arch flow control
Wheel covers (hub caps - convex)
Active wheel fairings
Secondary wheel covers / arches
Air curtains
1-5
4
5
3
5
5
5
3
4
3
3
4
4
3
5
4
5
3
5
3
3
4
5
5
5
3
4
4
1 Box
Maturity of the
Potential aero
Vehicle safety
Predicted cost
Manufacturing
Total
technology
advantages
regulations
Comments
mark
1-5
1-5
1-5
1-5
1-5
5
5
5
4
4
27
2
5
1
3
4
20
2
3
2
3
4
17 3 box
5
5
3
5
5
28
2
3
4
4
3
21
5
5
1
5
5
26
2
3
4
2
1
15
1
4
3
3
5
20
3
3
4
3
4
20
3
2
5
3
4
20
4
3
3
3
4
21 3 box
5
4
3
4
5
25
2
2
4
2
3
16
2
3
3
4
1
18
1
4
4
3
5
21 3 box
5
4
2
4
5
25
5
3
3
4
5
23 2 box
4
4
4
4
5
26 2 box
2
2
5
2
3
17 2 box
4
3
5
4
5
24 2,3 box
5
4
2
4
5
24 2,3 box
4
5
4
4
5
27 2,3 box
5
4
5
4
5
28
5
4
2
5
5
26
3
3
5
4
5
23 3 box
4
4
4
4
5
25 2,3 box
4
4
5
4
5
26
Task 12.3 – Conceptual Packaging Study to
Exploit Low Carbon Architectures (CU Lead)
test
Idea
Visualise
Task 12.3 – Steps in Implementation
Idea
test
Task 12.3 – Steps in Implementation
Concept
visualise
Task 12.3 – Steps in Implementation
Idea
Visualise
test
Concept
Task 12.4 – Conceptual Vehicle Styling/
Aerodynamic Performance Integration
(CU Lead)
Using the different components as an aerodynamic
toolbox for developing concept vehicles
Task 12.4 – Implementation
Task 12.5 – Aerodynamic
Simulation/Testing Process (MIRA Lead)
Background
 Initial survey gave areas of research:
 Base pressure recovery
 Wheels and wheel arches
 Performance simulations on EV’s (Ricardo)
 benefits of drag reduction over several drive
cycles
Task 12.5 – Aerodynamic
Simulation/Testing Process
Programme
 CFD (CU & MIRA)
 Full scale testing at MIRA (All)
 + Benchmarking
 Model scale testing (Outsourced to the 3 Universities)
 Aero process development (MIRA)
 Performance simulation & prediction (Ricardo)
 Drive cycle analysis
 Effects of drag reduction
 Validation of findings (All)
 Concept and feasibility of solutions (CU)
Task 12.5 – Programme:
CFD, Scale Models, and Vehicles
Method
CFD
&
scale
models
CFD
FSWT
MG FSWT
Location
MIRA
France
GIE S2a
Model
Scale [%]
Status
Mair body
-
Complete
MIRA Ref Car
-
Ongoing
MIRA/JLR
X351(XJ)
-
Ongoing
MIRA
Small MPV
-
Ongoing
Tata LCVTP
30
Complete
Rotating wheel rig
 80
Complete
Durham Uni
Bluff body (Ahmed)
25
Complete
Loughborough Uni
Windsor /Audi A2
25
Nr Complete
Coventry Uni
Model WT
(External
Research)
Method
Location
Cranfield Uni
Model
Status
Small MPV (Audi A2)
Nr Complete
Freelander
Complete
MIRA Reference Car
Nr Complete
X351 (XJ) Aerobuck
Ongoing
Audi A2
November 11
X351(XJ) Aerobuck
November 11
Full scale
models &
Vehicles
Task 12.5 – Base Pressure Recovery
On Basic Models – Ventilated Cavities
Durham Uni
•Ahmed body with ventilated base cavity.
•Baseline square-back configuration
•Effect of cavity depth for:
•
•
•
•
Solid walled cavity
Ventilated cavity with slots
Modified slot geometry
Model tested in ground effect and
freestream
•Particle Image Velocimetry (PIV) base
flow measurements
•Pressure measurements in cavity
Task 12.5 – Base Pressure Recovery
On Basic Models – Rear Taper
Loughborough University
• Windsor body with boat-tailed upper rear
body (rear body taper)
• PIV base flow measurements
• Pressure measurements on
boat-tail and base
PIV results
(Particle Image Velocimetry)
Task 12.5 – Scale Model WT Testing
Cranfield University
LCVTP model
0.280
0.270
0.260
0.250
Cd
0.240
0.230
0.220
0.210
Baseline
1° Floor
4° Diffuser
Wider Top
Body
Wiper recess Rear Wheel Front Wheel
blanked
Arch Blanked Spoilers fitted
(20x40)
Task 12.5 – CFD (CU) - Mair Model
Coventry University
 Mair body study (aspect ratio L/H, W/H, backlight
angle, boat tailing) - Complete.
 MIRA Reference Car (backlight angle, boat tailing, base
plate)
 Scanned surfaces from W/T model
Task 12.5 – CFD (CU) - Mair Model
No of afterbodies
0
0
2
4
6
8
10
-0.02
12
70 deg
backlight
experiment
-0.04
experiment round
edges
-0.06
quater model k-ε
quater model k-ω
-0.08
half model
quater model k-ε
ΔCd
-0.1
C70 k-ε
-0.12
Mair body: Change in Cd with afterbodies
Task 12.5 – CFD (CU) - MIRA RC
•MIRA Reference Car
• Validating CFD with wind
tunnel tests
• MIRA reference car model
morphing and testing through
CFD
•Scanned from MIRA FS model
•Correlation with FS wind tunnel
tests
• Within 5% of FSWT result
Task 12.5 – CFD (MIRA)
Jaguar XJ
Full vehicle analysis of Jaguar XJ and small MPV
Wheels, wheel arches and base pressure recovery
techniques
Task 12.5 – Full Scale Testing Small MPV
•Full Scale Wind Tunnel Testing at MIRA
•Development programme carried out
•Cd reduced from 0.29 to 0.21
Progression of CD During WT Session
0.290
0.280
0.270
0.260
CD
0.250
0.240
0.230
0.220
0.209
0.210
0.200
Standard
Production
Car
Wheel
Covers on
Flat Floor
Fitted
Front Intakes All Front End Door Mirrors Underfloor
Closed
Vents and
removed
Wheel Arch
Gaps Sealed
Blanking
Modification
7° Diffuser
30mm Front
65mm
Wheel
Extrusion
Spoilers
Tailgate Box
Cavity
Wheel /Sill
Panel
Task 12.5 – Full Scale Testing MIRA Reference Car
 The drag from the rear surfaces of a vehicle can account for more
Drag Coefficient Percentage Reduction
MIRA Reference Car, Squareback
Reduction >
Drag Coefficent change, %
8.0%
6.0%
4.0%
2.0%
0.0%
0.00
0.10
0.20
0.30
0.40
0.50
-2.0%
< Increase

than one third of total vehicle drag
Conventional methods and new concepts to increase base pressure
are being explored
-4.0%
-6.0%
-8.0%
-10.0%
-12.0%
Base Plate Offset, x/H
6.4% Drag Reduction
83% Base
66% Base
51% Base
38% Base
38% Base - Cut Out
Task 12.5 – Full Scale Testing Jaguar XJ
 Reducing wheel and wheel-arch drag (approximately a quarter of


the overall drag)
Annular rings can be more effective than using discs
For the X351 blanking the outer 35% of face area (shown) reduced
drag by 2%
Task 12.5 – FSMGWT S2A results
• Validation tests with a moving ground plane
• S2A wind tunnel at Paris used for this evaluation
• Provided the opportunity to evaluate modifications designed in fixed ground
plane wind tunnel
• Moving ground plane tests gave similar drag reduction results to the earlier
work, thus providing further confidence in the design concepts
• Detailed results are available in the project reports
Process development (MIRA)
 CFD - OpenFOAM process fully
developed for external aero
application
 Correlated with wind tunnel
data to examine complex
scenarios
 Large Volume Airflow Visualization (LVAV) - Several wind
tunnel tests used to show bubble flow visualization (achieved
at wind speed in excess of 20m/s)
 Transient, with surface mounted microphones pressure
measurements : progressed with work ongoing
Task 12.6 – Implementation and Evaluation with
Generic technology validation Vehicles (JLR/Tata Lead)
Effect of aerodynamic improvements over legislative and real world drive cycles
• Ricardo’s V-SIM software used to perform drive cycle analysis of EV’s
> Range of Cd and frontal areas
> Three different vehicle segments (A, C, E)
• Effect on Electrical energy consumption and EV range
• Effect of aerodynamics on potential
regenerative braking energy
• 8 different drive cycles analysed including:
> European legislative cycle (NEDC)
> US legislative cycles
> Real world Artemis cycles
Task 12.6 – Effect of aerodynamic improvements
over legislative and real world drive cycles
• Improvements gained vary with drive cycle and vehicle type
• Larger gains are on high speed cycles where aerodynamic loads
•
•
are dominant
> Low speed urban cycles are largely unaffected
The potential for regenerative braking is increased by
improving the vehicles aerodynamic drag
> City cycles have the largest potential for regenerative
braking but the increase by improving Cd is small
Smaller, lighter vehicles see a greater percentage gain by
improving vehicle drag
Aero ‘Design’ Manual
• Assumptions
> Passenger cars, light commercials, sports, SUV, etc
> SME’s, Niche vehicle manfufacturers
> Level: entry, assuming some engineering knowledge,
•
student
> Content from WS including illustrations
Topics/sections
> Intro, basics of drag
> Design for low drag
> How to do it
> Effects on fuel consumption, energy use (EV)
> How to get help