To Win Gold, US Swimmers Must Go with the Flow
GW Flow Dynamics Researchers Work with USA Swimming
to Improve Future Olympic Team Performances
The gun sounds and lean, muscular figures plunge into the water. They
vanish beneath the surface, kicking their legs in unison and moving swiftly
underwater with an ease that belies the furious effort exerted. The crowd
roars, but for the figures below all is silent. Precious seconds pass,
and finally heads begin to break the surface. One head emerges in front
of the rest. This margin is perhaps in the hundredths of seconds
but in Olympic swimming that is often enough to turn silver into gold.
GW engineering professors are using their expertise in computational fluid
dynamics (CFD) and computer animation and visualization to ensure that
US athletes are using the most efficient swimming techniques to help bring
home the gold from the 2008 Olympics in Beijing. GWs Flow Simulations
and Analysis Group (FSAG) is researching water flow past a swimmer and
the effectiveness of typical swimming strokes. The goal is to help find
the perfect stroke that maximizes thrust and minimizes drag, giving the
US a competitive advantage and improving the medal count for US swimmers
in future Olympics.
For the first time, we are really trying to introduce a big component
of cutting-edge science into competitive swimming, said Rajat Mittal,
associate professor of engineering and applied science in the Department
of Mechanical and Aerospace Engineering, who leads the project along with
James Hahn, professor of engineering and applied science in the Department
of Computer Science, from the Institute for Computer Graphics.
Interestingly enough, the genesis of the collaboration between USA Swimming
and GWs FSAG stems from previous research into how fish, not humans,
maneuver through the water.
More than a year ago Mittal began work with researchers from Harvard University
and MIT on a project for the Office of Naval Research (ONR). The goal
of that research is to design mechanical pectoral fins, much like those
of a fish, and attach them to autonomous undersea vehicles (AUVs) to provide
the vehicles with greater maneuverability and stealth characteristics.
The Navy uses AUVs during reconnaissance missions, such as mine sensing.
A Harvard zoologist is working with the actual fish and GW is building
and testing computer models of the pectoral fins to analyze their fluid
dynamics. After conducting their portion of the research, GW and Harvard
will provide the ideal size and dimensions of the pectoral fin to MIT,
who will build a working prototype of the fin.
The ONR work got Mittal to thinking. I asked myself, is there something
else we can use this research for that will not only be interesting but
will capture the imagination of our undergraduates? Mittal recalled.
Given the fact that fluid dynamics of fish swimming has many commonalities
with the fluid dynamics of human swimming, he decided to see if USA Swimming
had any interest in pursuing such research. As it turns out, Mittals
timing could not have been more perfect.
Mittal contacted USA Swimming and was directed to biomechanics coordinator
Russell Mark. My face lit up when Rajat called, Mark laughed.
It was really fortunate Rajat got in touch with us because the capabilities
he had were exactly what we were looking for.
In recent years, USA Swimming has conducted some limited scientific research
into fluid dynamics. With countries including Japan and Australia and
companies like Speedo beginning to undertake more sophisticated scientific
research, USA Swimming wanted to move forward with its own study, even
though large-scale research projects are not commonly conducted in the
swimming world. However, after analyzing the previous experience and research
capabilities of GWs FSAG, USA Swimming decided to move forward with
the project. As Mark put it, USA Swimming has always supported this
project, knowing that it has more potential to influence the sport of
swimming than any research in decades.
Both parties agreed to focus the research on the dolphin kick, the name
given to the leg motion swimmers use underwater at the start of a race,
when they keep both of their feet together and kick their legs up and
down. While there is a good possibility USA Swimming will eventually expand
its research to study different strokes and then the whole body, the dolphin
kick provides a good starting point for two reasons. First, the fluid
dynamics of the dolphin kick are easier to study since this stroke occurs
away from the waters surface, which increases the chances that the
results of the research can be incorporated into the US training regimen
prior to the 2008 Olympics. Secondly, the dolphin kick is such an important
component of competitive swimming. As Mark pointed out, in a 100-meter
race up to 30 percent of the total distance can be covered while the swimmer
is underwater using the dolphin kick.
At the initial stages of the research USA Swimming provided full-body
laser scans of top US swimmers Lenny Krayzelburg and Gabrielle Rose and
a video of record-setting University of California swimmer Natalie Coughlins
dolphin kick. Yet, Mittal and Hahn had to combine the information provided
by the static three-dimensional shapes from the laser scans with the motion
given by the two-dimensional video to generate a moving three-dimensional
virtual swimmer. Our challenge was to make the video come alive
as a three-dimensional object, Hahn explained.
To do so, Hahn inserted a digital skeleton into the body scan, and matched
the video frame by frame to equate the movement of the full-body scan
with Coughlins movement in the video. This process, called motion
capture, is similar to the techniques that are used to develop animated
movies in Hollywood. Hahn had created a 3D computer model that could be
made to move like the real swimmer and can be studied in ways that a traditional
video image could not.
Using his experience working with fish, Mittal has been able to simulate
flow past the body scans of Krayzelburg and Rose. Yet, there are many
different movements and body positions involved in swimming that remain
to be studied. In order to provide USA Swimming with the best information,
Mittal and Hahn are coordinating their work with researchers at Rutgers
University, who are handling the experimental components of the project.
However, this research is very complex and there is much work to be done.
While the dolphin kick may seem relatively simple, using computers to
create a lifelike animated model and studying the fluid dynamics surrounding
that model is not a simple process. The various components of this project,
especially the elaborate simulations, will require thousands of hours
of processing time on the FSAGs supercomputers.
Even after several years of study and analysis, Mittal and Hahn do not
expect to have all the answers for every swimmer. Intangibles such as
an athletes psychology and motivation can impact performance in
ways that computers can never hope to model or predict. There will
always be some level of individuality in terms of physiology, body type
and strength, but there is more commonality among great swimmers,
Mittal believes that in the long-term, a stroke should really be
customized to an athlete based on body size and structure.
USA Swimming eventually would like to see all athletes benefit from the
research and knowledge about the optimal stroke techniques. In the near
future the proving ground for this research will be leading up to and
during the 2008 Olympics. The only way this analysis is a success
is if its applicable, said Mark. This is not just a
science project; we are really trying to have an impact.
What kind of impact this research has will be seen on the medal podiums
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