Software CAE &

The powertrain design software and CAE newsletter of Ricardo
Characterizing the Range Rover and
Range Rover Sport using WAVE
Jaguar Land Rover’s Simon Worledge of the Powertrain NVH department faced
a challenge when designing different sound signatures for the Range Rover and
Range Rover Sport, both of which share the same drivetrain architecture. WAVE
software helped tackle the problem
Virtual engineering in the form of CAE software
has been with us for some time now and it is a
given that systems are modelled prior to physical
prototyping, saving time and money. Yet despite
the relative maturity of simulation techniques,
it is an area of engineering which continues
to develop. This is partly due to the improved
functionality of software but also because
simulation is a voyage of discovery where
experience plays a big part in exploiting the
power of software tools to the fullest.
At the Ricardo Software European User Conference
held in Ludwigsburg, Germany, in April of this year,
Simon Worledge of Jaguar Land Rover Powertrain
NVH gave an overview of how exhaust systems
were developed for the new Range Rover and
Range Rover Sport models using WAVE.
One platform, two very different vehicles
Prior to the introduction of these new-generation
cars, the outgoing models were actually quite
different entities in that the Range Rover Sport
was not based on the Range Rover, but the Land
Rover Discovery. In contrast, both of the new
vehicles are based on the company’s D7u platform
which in turn, is part of Jaguar Land Rover’s
Premium Lightweight Architecture.
Both the Range Rover and Range Rover Sport
have all-aluminium bodyshells where the previous
vehicles were built from steel. The new models
are not only the largest automotive aluminium
bodyshells in the world but each side panel is the
largest one-piece single aluminium pressing used
on any passenger vehicle worldwide. The vehicles
are both completely different to their predecessors
structurally, the Range Rover weighing 420 kg less
than the outgoing model. The outgoing vehicles
In this Issue
The new Range
Rover Sport (right)
and Range Rover
(page 3) are based on
the D7u platform – a
key challenge for the
NVH team was to
provide the required
sound quality and
differentiation
from a common
exhaust layout
Pages 1-3 Sound quality
How Jaguar Land Rover used Ricardo
WAVE software to create the right
sound for the Range Rover and
Range Rover Sport
Pages 3-4 Exhaust vibration
Independent engineering specialist
Martin Unbehaun uses WAVE and
FEARCE to eliminate unwanted
vibration from gas excitation
Pages 4 Application Engineering
Ricardo Software launches a new
service to help licensees maximize
their effectiveness and return on
investment in CAE
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Issue 1 2014
Software&CAE
Range Rover and WAVE
Range Rover Intermediate Can
Fully developed
CAD model
Broadband high
frequency attenuation
of engine "crackle"
– mainly empirical
development after
WAVE confirmed
unnecessary for order
control
WaveBuild3D
model
The modelled
perforated baffle
had minimal
acoustic benefit
compared to the
requirement to
exclude any pack
material from the
slipjoint area
shared common power units, the flagship being
the V8 5.0 supercharged engine, but both were
equipped with unique exhaust systems with
intrinsically different sound quality and character.
A key requirement for the two new vehicles was
product differentiation. As both share not only the
same architecture but the same exhaust layout,
this was to prove a challenge. Both vehicles have
very different characters, something that should
be reflected in their sound signatures. The Range
Rover represents the pinnacle of refinement but
the Range Rover Sport, while remaining luxurious
and refined, needed that edge to the exhaust note
befitting a sports vehicle.
The Land Rover engineering teams work according
to quite specific character definitions given to
individual vehicles. In this case, the Range Rover
should have “effortless delivery of power with
imperious isolation,” while the Range Rover Sport
should convey a character that is “direct, powerful
and purposeful.”
Sound engineering
The NVH teams translate these messages into
hard technical facts. At the higher rev ranges, the
Range Rover has no requirement to produce a
‘crisp, edgy crescendo’ whereas the Range Rover
Sport does. At lower engine speeds the Range
Rover has a complete absence of booms but gives
a subtle acoustic ‘reward.’ The Range Rover Sport,
on the other hand, is quite different at the low
engine speed range with dominant fourth and subfiring orders giving a ‘burble and an overt promise
of performance.’
Initial concepts were based on muffler boxes derived
from Jaguar luxury saloons. Although performing
well in the original saloon applications, WAVE
analysis soon revealed that the designs would not
be an ideal match for the bigger cabin space of the
SUVs. “When we finally got hardware produced, it
wasn’t quite what we needed. The back box was
fairly complex with a bypass valve, we had flow
issues and it was inherently prone to high frequency
broadband gas rush noise which didn’t give the
impression of refinement,” explains Worledge.
Simulations for the front box produced sounds that
were too unrefined and the small gap for mixing gas
between chamber and pipe produced unsatisfactory
levels of back pressure.
With that much established, it was back to the
drawing board, starting with the basics to examine
the underlying order structure and the extremes of
available tuning options. With V8s, Jaguar Land
Rover focuses on four primary orders for target
setting and engineering: 1.5E, 2.5E, 4E and 8E.
Because the engine is a V8, 4E will always be
dominant but increasing the ’half’ order content
would give the Range Rover Sport exhaust note the
more complex character it needed.
“We control this feature by how we mix the gases
early in the system,” explains Worledge. Starting
with the Range Rover and taking a fully mixed
approach, a new and bigger front can of 4.9-litre
capacity was created in WaveBuild3D then fully
developed as a CAD model. Significant work was
done using CFD to optimize the main duct and
minimize back pressure. The addition of a small
Helmholz resonator on the main central duct
proved useful, attenuating a fourth order peak quite
dramatically by around 10dB(A).
“Although in the WAVE model an intermediate
can was not needed, in physical testing the
use of one showed promise for mid to high
frequency attenuation so we kept it in place for
completeness,” continues Worledge. The can was
designed using the same techniques and was
much simpler than the front unit with two parallel
perforated pipes. The rear can was a much simpler
design than the very first model based on Jaguar
designs, with a ‘Perf ‘n’ Pack bomb – a chamber
filled with absorptive packing material, through
which the main exhaust line passes – at its centre
to deal with high frequency noise and flow noise
attenuation. A long, relatively small diameter
tailpipe gave good low frequency attenuation
and a pressurised Helmholz resonator helped
with specific boom control. “This resonator gave
significant fourth order control at low cruising
speeds and this extrapolates back to low rpm,
giving a high level of refinement in the idle region
and no unpleasant booms in the cabin,” says
Worledge.
When the finished results were compared to the
WAVE predictions, the correlation, though not
perfect on three orders, matched well on the fourth.
“I have a suspicion that the lack of correlation is
due to the high level of packing in the centre box,”
explains Worledge. The results are measured using
a microphone positioned 500mm from the tailpipe
at an angle of 45 degrees to one side. The virtual
microphone is mounted in the same position within
WAVE.
A more sports-like sound quality
The Range Rover Sport required a different
approach to reflect the vehicle’s sportier character.
Two cans, front and rear, were modelled in
WaveBuild3D with no intermediate can. Again,
the capacity of the three-chamber front can was
2 Ricardo Software & CAE • Issue 1 • 2014
Range Rover and WAVE / Exhaust Vibration
A more radical version was tried too, the front
box having the stainless steel wool removed
from one chamber and five 3.5 mm mixing holes
added to each duct in the centre chamber. These
perforations softened the effect slightly, the sound
otherwise lacking subtlety. Underfloor pipes were
increased in diameter to 60 mm. The rear box
retained the basic form but was given two tailpipes
and a more conventional resonator. One tailpipe
incorporated a butterfly valve allowing the exhaust
to demonstrate a duality to its signature.
4.9 litres but instead of full mixing, two ducts ran
straight through in parallel, giving an unmixed
system. The first and third chambers were packed
with stainless steel wool and each duct perforated
at the opposite end from the other (one perforated
in the first chamber and the other in the third).
In the rear can, the Perf ‘n’ Pack bomb was deleted
and the effectiveness of the Helmholtz resonator
reduced by decreasing the size of the neck. The
tailpipe diameter was increased to 75 mm. In
contrast to the Range Rover, it was desirable to
retain the order content coming through and for it
to be audible from the tailpipe. Using WavePost’s
Frequency Network Display, Worledge identified
a 600 Hz mode across the front chamber of the
rear box: this gave a much stronger resonance at
the exhaust orifice than the initial attempts, which
centred only on tuning the tailpipe length, resulting
in the crisp definition of the sound character. On this
occasion, the physical performance of the finished
system correlated closely with the WAVE predictions
indicating just how powerful WAVE can be in early
simulations.
With the valve closed for relaxed cruising, the
exhaust gas exits the first pipe into a chamber via
perforations and exits via the second tailpipe, a
resonator helping to attenuate the sound. With
the valve open, the system becomes effectively
'straight through', emphasising the low frequency
range around the 1.5 and 2.5 orders, giving a rich,
deep, modulated sound.
However, this version was judged to be too
extreme for a mainstream product, and has been
held in abeyance pending a more suitable vehicle
package. Nevertheless, the other designs formed
the basis of the new Range Rover line-up’s sound
signatures, helping to make them among the most
desirable premium vehicles in the world.
Beating exhaust vibration
with WAVE and FEARCE
Gas excitation can cause deformation
and unwanted vibration in exhaust
systems. Independent engineering
specialist Martin Unbehaun has
discovered how to address this issue for
his clients using a unique approach and
Ricardo Software technology
Quite where vibration comes from in a vehicle
exhaust system is not always clear, but Martin
Unbehaun of Unbehaun Acoustic Engineering has
been looking at how a combination of WAVE and
FEARCE can be used more effectively than traditional
methods to measure an important aspect of exhaust
system design that has so far remained overlooked.
Traditionally, CAE analysis of exhaust systems has
focused on temperature, back pressure and tailpipe
noise using WAVE, detailed flow distribution using
3D-CFD, deformation and stresses arising from heat
Issue 1 • 2014 • Ricardo Software & CAE 3
Exhaust Vibration
strain, and road excitation and engine vibration,
using FE methods. But the one area that has been
overlooked until now has been that of deformation
and stresses caused by exhaust gas excitation.
“One day we found very strong vibrations in an
exhaust system at engine order 1.5 with a V6
engine,” explains Unbehaun. “The engine had
almost no vibration at that engine order but the
exhaust system itself had strong vibrations of up
Martin
Unbehaun
to six millimetres downstream from the flexible
coupling.” A V8 exhaust system was prepared with
short exits at the bottom of the downpipes. Vibration
further down the system disappeared, supporting the
theory that the vibration was caused by gas flow.
Three parameters were singled out for investigation:
average pressure, pulsating pressure and pulsating
flow. Measurements at the centre of the muffler
revealed an average pressure of 400 mbar. When
multiplied by the area, this extrapolated to a force
of 5000 N, or the equivalent of hanging a 500 kg
weight from the muffler. Pulsating pressure was
identified in curved sections of pipe (such as the
downpipe) equivalent to 145 N; a great deal of force.
Finally, pulsating flow velocities of 220 m/sec were
identified, creating forces in a curved pipe of 50 N.
The classical approach for measuring this was to use
WAVE and an FE simulation. The system took the
form of twin pipes leaving the engine and entering a
centre muffler, a single pipe exiting to a rear muffler.
The simulation showed exhaust gas entering the
centre muffler from one bank of cylinders, trying to exit
back in the opposite direction via the second branch
of the system, giving a very strong resonance in the
process. The forces can be calculated by exporting
the pressures and velocities into a spreadsheet. The
simulation was performed for steady and transient
states to calculate the level of excitation, a process
which requires much thought and hard work.
The new method adopted by Unbehaun is to apply
the WAVE temperature and pressure results to the
FE model in FEARCE by exporting to a cloud file. The
simulation produced a strong vibration of up to
3.5 mm, which corresponds to the measurements
found in a similar physical system.
The next stage was find out how best to minimize
the vibration. With an open bridge linking the
two pipes at the front of the system, the gas
resonance bypasses the main system and the
excitation is eliminated. The method was also
applied to assessing the effect of sound radiated
from the muffler due to vibrations. A combination
of the changed muffler shape and the open bridge
significantly reduced vibration and radiated noise.
It is early days yet, but the results are extremely
promising and Unbehaun is looking forward to
exploiting this new WAVE- and FEARCE-based
technique in his future client work, and correlating
results in more detail with physical testing.
Bespoke CAE support
Ricardo Software has launched a new
‘Application Engineering’ service to help its
software licensees maximize their effectiveness
and return on investment in CAE simulation.
The service has two distinct facets: helping
customers improve their deployment of CAE
through analysis process development, and
the execution of small simulation projects
using Ricardo Software products in order to
demonstrate different applications on live
design, development or research tasks.
“Customers are frequently telling us that they’d
appreciate support beyond the level of the
conventional user training model,” explains
For further information about Ricardo
Software productions and support services,
please contact:
application engineering manager John Foy. “As
the developer of the CAE products and a major
consulting business in its own right, Ricardo
is ideally placed to provide highly trained and
experienced engineers to demonstrate complex
applications or to configure CAE processes
designed around the specific needs of individual
clients.”
The benefits of this form of service can be
considerable, not least in exploring the possible
use of new software products or applications.
“The traditional approach to evaluating a
new product is to take an evaluation licence
and allow engineers who are unlikely to be
Software Sales: Software Support: Or visit experienced in its use to make an evaluation,”
continues Foy. “We can work with the client
before this stage, to assess precisely the CAE
products that will best suit their requirements,
and then demonstrate the software on live
projects. For a small investment, the client can
be up and running much more quickly and can
potentially yield a much better return on their
CAE investment,” he concludes.
The Application Engineering service is
available across the full range of Ricardo
Software CAE products. For further
information contact John Foy at
John.Foy@ricardo.com.
RS_Sales@ricardo.com
RS_Support@ricardo.com
www.ricardo.com
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