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Oilflow lines
over the body
colored by
dynamic
pressure
In 1896, when the French Baron, Pierre De Coubertin lobbied
to resurrect the ancient Olympic Games as a modern amateur
athletic event of sporting excellence, little did he know that one
day it would become the biggest event in the world, with an estimated
viewing audience of over half the Earth’s population. For
two weeks in Athens this August, the Games will come to Greece
once again for the XXVIII Summer Olympiad, and attention will
turn to the sportsfest where the elite athletes of the world’s nations
compete for personal and national glory.
For most events today, the difference between winning and
not winning a medal is usually a fraction of a percentage point
in overall performance. Given such a landscape, any legal and cost-effective
competitive advantage will be sought out by national
teams, individual athletes, and equipment manufacturers to gain
that extra edge. Two sports that tend to dominate the viewing
coverage throughout the Summer Games are swimming and track
and field, and it is in these sports that many of the closest performances
occur.
Speedo International Ltd, the world’s leading swimwear brand,
identified the potential for bringing CFD technology to the swimming
pool after reading an article in Fluent News (Spring 2000)
about Barry Bixler, a principal aerospace CFD engineer working
for Honeywell in Arizona. At the time, Barry had spent much of
his spare time working in his garage on a CFD analysis of the hydrodynamics
of swimming strokes for USA Swimming. Speedo’s Research
& Development team in Nottingham, England contacted Bixler
and Fluent Europe Ltd in Sheffield to see if it would be possible
to harness CFD technology to enhance their world-leading Speedo
Fastskin suit, which made headlines in 2000. At the time, it was
the world’s fastest swimsuit, in part because it mimicked the skin
of a shark. Swimmers from over 130 countries wore the swimsuit
in Sydney, where it revolutionized the swimming world by
contributing to over 80% of all the swimming medals, and swimmers
wearing the suit broke 13 out of 15 world records. Speedo
saw the potential of CFD-based fluid flow analysis to understand
swimming hydrodynamics, even though CFD had never been used
in swimwear development before. The wide use of FLUENT in other
sports such as Formula One motor racing and America’s Cup Yachting
convinced Speedo that it had the proper qualifications for their
sporting CFD challenge.
Pulsed water flow pathlines over the body colored by local static pressure
Visualization by EnSight
“The CFD modeling we have done has
been both challenging and extensive.
Using FLUENT, we have been able to
mathematically model a water flume on
our computers. We analyzed the flow
and obtained incredibly consistent and
accurate results. The CFD analyses,
combined with flume testing, enabled
Speedo to evaluate a huge number of
swimsuit design variables, and
eventually, we believe, obtain the
world’s fastest swimsuit.”
-Barry Bixler
CFD Consultant to Speedo
In March of this year, Speedo launched their new fast suit, Fastskin
FSII, at several high profile media events in Sydney, London, and
New York. The development of the suit, which they claim to be
the fastest in the world, has involved a collaborative team of experts.
CyberFX, the Hollywood-based body scanning and special effects
company behind the recent Spiderman, Matrix, and Charlie’s Angels
movies, was involved in the swimsuit’s development process from
the beginning. Its unique body scanning technology allowed Speedo
to create anatomically correct ‘virtual’ and ‘actual’ models of the
average male and female swimmer to provide the perfect base
upon which to test the suit. With the help of CFD modeling work by Bixler and the University of Otago Water Flume in New Zealand
(the lowest turbulence intensity flume in the world, capable of
producing very strong currents), Speedo R&D engineers were able
to show that the Fastskin FSII swimsuit they have developed increases
underwater speed by reducing passive drag by up to 4% compared
to the next best suit. Based on these findings, Speedo expects
the swimsuit to help elite swimmers (who all have access to Fastskin
FSII under FINA rules) to break even more world records in Athens.
Speedo Fastskin FSII swimsuit in action
Once the swimsuits were validated with the water flume trials,
the CFD software was incorporated into Speedo’s design process
to evaluate the drag and fluid flow characteristics around the male
and female swimmers for various flow scenarios. Bixler’s CFD work
allowed Speedo to simulate the flow around the virtual swimmer
bodies, thus making Fastskin FSII as hydrodynamic as possible.
During the swimsuit development process, the CFD models helped
to eliminate variability in the results so that Speedo could conduct
a greater number of tests and achieve more accurate results
than ever before. Moreover, CFD’s ability to visualize the details
of the water flow around the athletes revealed information that
had not been known previously. The results were used to guide
the position of the seams, gripper panels on the underside of the
forearms, and “vortex” riblets on the chest, shoulders, and back
of the suit. In addition, the CFD predictions of water flow over
male and female bodies helped to guide the positioning of different
patches of fabric and fabric coatings available to Speedo
to optimize the suits created for the different swimming events,
such as breaststroke and backstroke.
CFD simulation of water
flow over typical female
(top) and male (bottom)
elite swimmers in the glide
position showing contours
of shear stress (frictional
drag) on the swimsuit
region
The 'actual' scanned models that had been made into precision
mannequins were used in over 1,000 flume tests carried out
in Otago. The results supported the CFD findings that the new
Fastskin FSII full bodyskin is the fastest and most advanced performance
swimwear in the world. Engineers at Speedo believe that
they have now achieved a transfer of motor racing technical design
methodology to the hydrodynamics of swimming and swimsuits.
This is probably a first for a sportswear brand, and a milestone of
applied engineering to the complexities of ergonomic sports systems.
In the wake of Speedo’s new CFD design process, this
integrated technical design approach will almost certainly pave the
way for many other sports in the future, especially those dominated
by equipment aerodynamics and hydrodynamics.
Speedo’s customized
swimsuit colored
by CFD-predicted
frictional drag is
modeled at the
New York launch
Ultimately, however, the success of any swimsuit is in its acceptance
by the world’s leading swimmers and coaches. Speedo has
not been neglecting the interface with elite athletes, and has been
working with a group of swimmers from around the world to develop
Fastskin FSII. They have selected eleven elite swimmers, known
as the Speedo FSII Team, who are at the forefront of Speedo’s
challenge in Athens to evaluate the suit in pool performance tests.
The group includes the latest phenomenon from the US, 18 year-old
Michael Phelps. Phelps, who broke three world records and
won three gold and two silver medals at the 2003 World
Championships in Barcelona, will be wearing a Fastskin FSII in Athens
in a bid to match Mark Spitz’s famous record of seven gold medals
at the 1972 Summer Games. If successful, Speedo will pay Phelps
a cool one million dollar bonus. Performance tests by elite swimmers
on the new suit are taking place this spring, and will provide
the ultimate feedback in terms of performance increases to
be gained from this high-tech innovative swimming product.
Certainly, the temperature in the Athens swimming pool is heating
up already thanks to this exciting and pioneering use of CFD
by Barry Bixler and the Speedo R&D team.
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