10
Developing Rapid Turnaround Techniques in Aerodynamic
Development. Experiences with the Infiniti Emerg-E and
Beyond.
Geoff Le Good, Ivor Annetts, Troy Kenion
Abstract
The compact nature of concept vehicle programmes rarely provides an opportunity
for integrated aerodynamic development. For the Infiniti Emerg-E range-extended
electric sports-car project, however, the aerodynamic development of a running
demonstrator vehicle was included as part of the core styling and engineering
programme. In order to assess and contribute to the rapid iteration of the style, a
process was tailored to the specific timing and resource constraints of the
programme. In the time which has passed since the end of the Emerg-E project, the
process has been further evolved for application in automotive concept studies.
10.1 Introduction
The Infiniti Emerg-E was the outcome of a concept car development programme run
by the Nissan Technical Centre Europe (NTCE) [1]. Two versions of the car were
produced: the less-constrained “show car” (Figure 10.1) made its debut at the
Geneva Motor Show in March 2012 while the first of two fully functioning
“demonstrators” (Figure 10.2) ran for the first time in public at the Goodwood Festival
of Speed in June 2012 piloted by Formula One driver Mark Webber.
Figure 10.1: Infiniti Emerg-E Geneva Show debut - March 2012
The origin of the project was the involvement of NTCE in the REEVolution
programme which was funded by the UK Technology Strategy Board and designed
to help evolve range-extended and ultra low-carbon plug-in hybrid electric vehicle
technologies amongst UK-based manufacturers and suppliers. The lead OEMs
involved with the range-extended electric vehicle part of the programme were Lotus
and NTCE. Infiniti is the luxury brand of Nissan [2] and Emerg-E was conceived as a
means of demonstrating both visually and practically what future vehicle technologies
could deliver in performance whilst retaining dramatic styling. The demonstrator
vehicles were built with the aim of providing journalists with an opportunity to
experience the technology at first hand.
Figure 10.2: Infiniti Emerg-E Demonstrator debut – Goodwood Festival of Speed 2012
with Mark Webber and Early Track Running.
Under the collaborative REEVolution project, the cars developed by NTCE and Lotus
utilised a common platform, powertrain, steering, suspension and running gear from
the Lotus 414E programme. The Lotus version ran under a Lotus Evora body-style
while the Infiniti Emerg-E had a uniquely designed and developed body constructed
in carbon-fibre. As illustrated by Bateman and Kenion [3] the common architecture is
shown in Figure 10.3 and the key performance targets and powertrain specifications
listed below.
Figure 10.3: Common vehicle architecture
The performance targets were:
 Acceleration 0-60 mph (0-100kph) :
 Maximum Speed:
 EV Range:
 Full Range:
4 seconds
130 mph (210 kph)
30 miles (48 km)
300 miles (480 km)
The powertrain consisted of:
 Lotus 1.2 litre 3-cylinder I.C. engine capable of 35kW at 3500 rpm
 Evo electric AF130 generator
 360v battery with energy capacity of 14.8kWh
 X2 Rinehart Inverters with 100kW power rating each
 Xtrac single speed transmission (4.58:1 ratio)
 30 litre fuel tank
The Emerg-E project was undertaken by NTCE additionally to production vehicle
programmes and so support was engaged from Concept Group International Ltd
(CGI) for the design and manufacture of the show car and the two running
demonstrator vehicles, and from G L Aerodynamics for the aerodynamic
development programme. Both these companies also brought in specialist subcontractors to support their work. In the case of the aerodynamics programme,
specialist company TotalSim Ltd provided the CFD analyses. The project was led by
NTCE and supported by Nissan Design Europe staff from their London studio [4].
The small team of designers, modellers and engineers was located for the duration of
the project within a dedicated office, design studio and prototype build shop at
Concept Group International’s facility in Coventry [5].
This paper describes the approach taken in the aerodynamic development of the
Infiniti Emerg-E demonstrator vehicles and comments on the evolution of those
techniques in the subsequent 18 months.
10.2 Aerodynamics Development Strategy
The aerodynamics departments within most automotive OEMs usually have one or
more generic programmes which are designed to support corporate new-vehicle
development programme plans. Typically, initial work is undertaken to support
styling-studio activities by assessing themes and large-scale changes to body forms
and vehicle proportions. As the opportunity for styling changes diminishes with time
into the programme, the aerodynamicists’ focus may shift to: the optimisation of
details, component development - such as mirrors, spoilers and underfloor parts, the
optimisation of cooling flows, soiling and water management as well as aeroacoustics. The contribution of aerodynamics to a multitude of attributes is illustrated
by Hucho [6].
As a service function within manufacturers, aerodynamics departments make use of
a combination of experimental and computational tools to provide data and
recommendations to the Styling department and component design groups.
Aerodynamics departments rarely have design or release responsibility for
production parts. As a new-vehicle design matures and more CAD information
becomes available, small-scale and full-scale wind tunnel test properties and CFD
models can be updated and more representative assessments made of the
aerodynamic characteristics.
For the Infiniti Emerg-E aerodynamics programme, there was no requirement to
follow generic NTCE processes. Instead, the design of the aerodynamics programme
was influenced by: the overall project timing plan, the proposed two-weekly formal
styling review process, the good availability of detailed CAD information for the
vehicle architecture from the very start of the project and the indicated resource plan
from NTCE. The specified objective for the aerodynamics programme was to help
meet the performance targets listed above by providing feedback on designs to the
styling and engineering groups and guidance on further shape iterations. The
expected duration of the design programme was 6 months.
By the time at which G L Aerodynamics joined the project in March 2011, already
three styling themes had been developed in different Nissan studios and there was
shortly to be a styling review which would determine a single theme to be taken
forward for the rest of the project. Although the themes had been developed using
small-scale clay models these were unsuitable for wind-tunnel testing. However, 3D
scans of the models had been imported into computer-styling tools in order to create
CAD surfaces for all three themes. With the availability of these surface models and
the detailed CAD of the platform architecture it was decided to use CFD techniques
to ensure a comparative aerodynamic data-set was available for reporting prior to the
styling review and the subsequent decision on a single theme to be progressed.
Whilst there was no imposed restriction on the means of aerodynamics testing to be
conducted in this programme, a decision to rely principally on CFD analyses to also
support the single theme development was taken due to a combination of factors:
 that the original specified requirement was for a “simple” aerodynamic survey
of (an estimated) comparatively few style releases through the course of the
programme
 the only physical property intended to be built for the exterior style
development was to be a split full-scale clay model (one half being used to
develop the show car style, the other the demonstrator) – which was
unsuitable for wind tunnel work.
 the lack of time available to build a detailed full-scale wind tunnel test buck
In practice, the aerodynamics contribution to the project evolved from an initial
proposal of simple, rapid assessments of each style release against the programme
functional targets to become a more integrated role working closely with both the
styling and engineering teams to incorporate ideas and features as the design
matured.
In hindsight the ideal aerodynamics programme for the Infiniti project
been to have started earlier and to have run both a full-scale aerobuck
test programme with full 3D scanning support in parallel with even
analyses. However, the resource and budget requirement to run such a
would have been several magnitudes greater than actually utilised.
might have
wind tunnel
more CFD
programme
10.3 The CFD Methodology
For each test configuration a fully detailed model of the car was used. The CFD
model build was essentially completed in two stages:
 Underbody, engine bay and wheels
 External bodywork configurations
The final model was created by stitching the released body surface from the project
team (usually NURBS surfaces created in Autodesk Alias CAS software) to the
supplied CAD of the platform architecture shown in Figure 10.3 .
The mesh for each configuration was approximately 50million cells in size with a
surface edge length of 6.25mm. It took 16 hours for each run to mesh, solve and
post-process on a 48-core cluster.
All models were solved using TotalSim’s modified version of OpenFOAM
(OpenFOAM is a registered trademark of ESI). The flow was assumed to be
isothermal, incompressible and steady state. A ‘RANS k-omega SST’ model of
turbulence was used.
The standard test case set-up was for the car to be modelled as if running on an
‘open-road’ with moving ground and rotating wheels. The nominal test speed was
33.33 ms-1 (120 kph).
Later CAD configurations included modifications to the platform architecture as the
rear diffuser, front intake, front undertray were modified and unique cooling ducts to
the engine bay designed.
10.4 CFD Assessment of Three Initial Themes
The first aerodynamic contribution to the Infiniti Emerg-E programme was a CFD
assessment of the three initial styling themes prior to their review and the “Go For
One” decision programme milestone. The CFD models are shown in Figure 10.4.
The main challenge at this stage of the programme was the stitching of the styling
data to the first version of the platform architecture CAD. Despite the styling teams
working to the same package data, the body surfaces of all three models were not
ideally matched to the common platform. This was particularly the case in terms of
intake sizing and positioning but also there were several instances of the bodywork
intersecting or deviating from the platform design.
In order to create a “fair” aerodynamic comparison of the three themes, the initial
CFD model-builds took a total of 15 man-days to complete including the time to
generate test meshes, debug any issues and setup the automated post-processing.
Each subsequent model-build in the programme took a maximum of 3 man-days to
complete.
Figure 10.4: Initial Themes
One of the key advantages of utilising CFD analyses at this stage of the programme
was the opportunity to include not only the reporting of numerical aerodynamic
characteristics but also to include a wide variety of graphical outputs to illustrate to
the styling teams how and why the aerodynamic characteristics of their designs
differed. An example of the comparative data which was used in the reporting at this
first phase is shown in Figure 10.5.
Figure 10.5: Comparative Zero Total Pressure Plots Reported for First Three Themes
10.5 Single Style Aerodynamics Development
In automotive aerodynamics consultancy projects, it is often true that the plan which
is first envisaged for early concept and styling support evolves into a more complex
scheme but also hopefully more influential. This was true of the Infiniti Emerg-E
programme. Initially it was expected that a “simple” aerodynamic survey would be
conducted of selected released styles. However, the process soon changed to one
whereby aerodynamics was a key consideration of both the styling and engineering
programmes. This change was due to:

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The quality of information and speed of turnaround achieved with the
assessment of the initial 3 themes.
The NTCE project team leadership encouraging direct aerodynamic design.
Increased aerodynamicist presence in the studio and engineering office during
the early stages of work.
The interest and enthusiasm by both the styling and engineering teams to
incorporate aerodynamics recommendations and features.
It is worth highlighting that the increase of aerodynamics involvement was possible
because of the excellent working relationships formed at the start of the project and
the fact that most of the team were very experienced automotive designers and
concept engineers. The integration of aerodynamics into the style development was
evidenced by the designers keen to pose “what if” questions about features and style
changes as soon as they had ideas. Thus, instead of preparing results solely for
timed programme reviews, the aerodynamics programme became one of a constant
flow of design updates and CFD testing. “At shoulder” support was provided while
designers created new Alias models and engineers modified their CATIA CAD
models.
The integration into the design process also invoked changes to the CFD postprocessing output specification. At the start of the programme an “Output Menu”
spreadsheet was developed to specify the numerical data and illustrative pressure
and flow images required for each configuration. Initially a standard output for a new
test configuration would include approximately 50 images and videos together with a
table of aerodynamic force and moment characteristics data. As more work was
undertaken, more results were extracted from each CFD run including multiple drag
and lift breakdowns for individual components, flow rates for cooling ducts and
additional illustrative analyses such as cumulative drag and lift plots along the
longitudinal axis.
The single style development phase lasted, just over 3 months. In this time 45 mandays of CFD development were supplied in total creating 5 new complete styling
updates and 44 development runs based off these updates. Although most CFD
model updates were reliant on released CAD data from styling and engineering,
some other simple modification proposals were created using other CAD and
morphing software. These modifications (e.g. boot flicks and spoilers) took only an
hour or two to construct whilst more extensive changes (such as bodywork panels)
took up to a day to complete.
Amongst the many Aerodynamics design requests incorporated were:
 Inclusion of a rear spoiler to enhance high speed handling but with minimised
drag penalty. This was the result of several design iterations from a simple 2D
aerofoil section to a more complex style which, importantly, carried the
characteristics of the whole car (see Figure 10.6)

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

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

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Double-diffuser rear underfloor. This concept evolved from a styling
suggestion made during a discussion on how to extract more underbody
performance. The design included a re-routing of the range-extender engine
exhaust to enhance the flow performance.
Revised door mirror shape and position to reduce drag and enhance flow into
the rear haunch intake.
Incorporation of brake cooling duct upsweeps into the front underfloor.
Addition of wheel-spoilers.
Modification to sill profiles.
Larger front splitter incorporated into front bumper.
Revised front bumper cooling apertures and grille blanking.
Revised front intake ducting geometry to assist cooling airflow (See Figure
10.7).
Modified rear cooling duct geometry to reduce flow losses (See Figure 10.7).
Repositioned engine-bay outlets.
Figure 10.6: Rear Spoiler Developed as a fully Styled Component
Figure 10.7: Aerodynamics contribution to Cooling Flows
The images created in the CFD post-processing and rapid feedback of results were
instrumental in designing, optimising and verifying all of the listed features above.
Despite the successes there were several challenges and ‘blockages’ in the process
which compromised some of the turnaround times and, perhaps ultimately, limited
the number of CFD runs undertaken (an aerodynamicist’s desire is always for more
test data from which to analyse results and make recommendations !). The first was
that although it was simple to add more post-processing output, it took a little longer
to compile, analyse and feedback results. The second and more significant concern
was that the released CAD data, particularly the upper-body styling surfaces required
additional time to repair, trim, gap-fill and stitch surfaces. During the programme the
issue as to where was the most efficient location for surface repair to be conducted –
i.e. at the Styling or CFD end was never fully resolved, but it remained a timeconsuming concern.
At the end of the single theme design stage the overall impression was of a more
extensive, integrated and contributory aerodynamic process than had been expected
originally.
During the build phase of the two demonstrator vehicles further on-site aerodynamics
support was provided to over-check component designs and to monitor build quality
and fit and finish. When the first demonstrator build was complete, except for final
trimming of the interior, the car was taken to MIRA for a full-scale wind tunnel test as
shown in Figure 10.8. Although this was used confirmation test of the aerodynamic
characteristics it was also used as filming opportunity to support the launch activities.
Figure 10.8: Wind Tunnel test of Demonstrator at MIRA
10.6 Evolution of the CFD Process in Subsequent 18 Months
In the time since the completion of the Infiniti Emerg-E project G L Aerodynamics and
TotalSim have continued to evolve the CFD development process for concept and
early styling studies where fast turnaround and assessment of multiple configurations
are required.
The updates and improvements to the TotalSim CFD analysis process have
included:
 Increased hardware performance has reduced solution time by 30% with a 60
million cell model typically taking 12 hours to mesh, solve and post-process.
 Increased amount of hardware allows a single configuration to be run at more
flow conditions (wind yaw, speed, car attitude).
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Greater proportion of the process is automated. This leads to faster turnaround and frees up engineer’s time to spend on analysis (more added value).
Automated model checking to minimise human errors.
Automated ride height changing makes it easy to test multiple attitudes and
heave positions.
More physics can be modelled as standard e.g. thermal, ‘true cornering’ flow
simulation and transient DES analysis.
As part of the CAD creation process more use is being made of direct morphing of
the CFD model to help create systematic geometry changes which are typically used
in detail optimisation in wind tunnel testing. This necessarily creates more CFD
configurations than might have been created in the past but the processing cost and
speed makes this a comparatively efficient process if a parallel “configuration
stacking” computing approach is taken rather than replicate the series development
necessitated in wind tunnel testing. Geometry morphing typically takes 1 or 2 hours
to setup but then multiple cases can be created. The number of configurations is now
limited by available CPU not man-time to create. For a configuration optimisation
series, routinely 20 designs are initially considered. Workload planning is now also
key ingredient in this approach.
In addition to the opportunity to test more configurations and faster, the process has
been further enhanced by the specification of more post-processing imagery in the
extended output menu spreadsheet. The exact quantity of output data depends very
much upon the programme being undertaken, but as an example, for a concept
exterior body development project the standard dataset per run can include around
180 images and 20 animations of flow regimes, pressures, iso-surfaces and near wall
velocities etc. Individual component breakdowns of drag and lift and “close-up”
images of flow characteristics extend the output quantity further. With this opportunity
for vast amounts of output data the task of specifying its format has become
increasingly time-consuming. Sometimes this can be upwards of one or two mandays depending on how views are created and specified. The consequential add-on
to this is the additional scripting of the CFD post-pro output.
Solutions to two further challenges are under development. The first is in finding a
rapid means of reporting and assessing the output data. With so much numerical and
illustrative data now becoming available it is essential to find an efficient and reliable
means of at least some automated processing, plotting and comparing configuration
results. The second and newer challenge is to evolve a process which allows results
from the aerodynamicists’ initiated configurations, particularly those of optimised
configurations, to be supplied not only as numerical and graphical data but now also
as useable CAD geometry for rapid integration into styling and component design
processes.
10.7 Conclusions
The Infiniti Emerg-E programme provided an opportunity not only to gain expertise in
the aerodynamic considerations for range-extended electric vehicles but also, as a
valuable spin-off technology, to evolve processes for the application of CFD
techniques in early automotive styling and concept work. For this latter contribution,
the primary requirement was for rapid turnaround of analyses to answer “what-if”
questions to potential shape and form changes as well as proposing design changes.
This was successfully achieved to meet the demands of the Emerg-E programme but
has subsequently been developed further for application in conventional projects.
However, whilst the cost and time-efficient computing element has provided much of
the opportunity for this application in vehicle programmes, including the output of
huge quantities of numerical and graphical data, more development of the CAD input
and data processing techniques are required in order to fully exploit the complete
process.
10.8 Acknowledgements
The authors wish to thank: NTCE for permission to publish this paper, Lee Courtier
and his CGI engineering team for their support and accommodation of the
aerodynamics design concepts and change requests; Simon Cox and his CGI styling
team for their interest and enthusiasm for their inclusion of aerodynamics features in
the design; the staff, modellers and technicians at CGI for their accommodation,
hospitality, support and interest during both the design and vehicle build phases. In
addition, the authors wish to thank Tim Dunn (NTCE), Bob Bateman (NTCE), Dipesh
Solanki (NTCE) and Dean Claridge (Nissan Design Europe) for their help and
interest in the integration of the aerodynamics development programme within the
Infiniti Emerg-E programme.
10.9 References
[1] Nissan Insider – Behind the Scenes at NTCE: http://nissaninsider.co.uk/behindthe-scenes-at-ntce/
[2] Infiniti brand website: http://www.infiniti.com/gb/stories/our_brand.html
[3] Bateman, B. and Kenion, T. – “Infiniti Emerg-E” presentation to IMechE branch
meeting, 9th April 2013, University of Warwick
[4] Nissan Design Europe: http://www.nissan-global.com/EN/DESIGN/BASE/NDE/
[5] Concept Group International Ltd: http://www.concept-group.com/
[6] Hucho, W.H. – “Aerodynamics of Road Vehicles”, 4th edition, pub: SAE 1998,
ISBN 0-7680-0029-7, CH1 pp2-57