From NASA, drag reduction for swimmers

NASA – NASA Know-How Helps Athletes Rocket Through Water

NASA Know-How Helps Athletes Rocket Through Water

David E. Steitz
Headquarters, Washington

Kathy Barnstorff
Langley Research Center, Hampton, Va.

Feb. 12, 2008



NASA Know-How Helps Athletes Rocket Through Water


Va. – When a swimsuit manufacturer wanted to create a better fabric for
competitive swimmers, it sought out some unlikely experts — aerospace
engineers at NASA’s Langley Research Center in Hampton.

has decades of experience in fluid dynamics and drag reduction.
However, aerospace engineers usually concentrate on the element through
which airplanes and spacecraft fly, not the liquid through which
swimmers travel. Still, some of the science is similar.

and water are both what are referred to as Newtonian fluids,” said
Steve Wilkinson, a researcher at Langley’s Fluid Physics and Control
Branch. “Air has different fluid properties than water, including lower
density and viscosity, but it still obeys the same physical laws of

That fact led Warnaco Inc. of New York, the U.S.
licensee of the Speedo swimwear brand, to seek use of a NASA wind
tunnel at Langley to test swimsuit fabrics that may be used by athletes
in international competitions.

“We evaluated the surface
roughness effects of nearly 60 fabrics or patterns in our small
low-speed tunnel, which is perfect for this purpose,” Wilkinson said.
“We were assessing which fabrics and weaves had the lowest drag.”

Reducing drag helps planes fly more efficiently, and reducing drag
helps swimmers go faster. Studies indicate viscous drag, or skin
friction, is about one-third of the total restraining force on a
swimmer. Wind tunnel tests measure the drag on the surface of the

Wilkinson and other NASA researchers usually spend
their time studying drag reduction for airplanes. They even have worked
on drag reduction technology for boats, including an America’s Cup
winner in the 1980s. This expertise is one reason Speedo chose to work
with NASA.

“This is the first time I’ve tested a fabric and
there were some challenges involved,” said Wilkinson. “I think we’ve
done a really good job with the help of Speedo in coming up with a
protocol that enables us to test these fabrics with ease and precision.”

The materials tested come in the form of tubes. Wilkinson stretches the
tubes over a smooth, flat aluminum plate and then secures the edges
with smooth metal rails and tape to form a precise rectangular model
shape. Wilkinson runs the material through a number of wind speeds and,
with the help of sensors, measures drag on the surface. Under a
reimbursable agreement, NASA turns the wind tunnel data over to Speedo
for their use.

“It turns out to simulate a swimmer in the water
at about two meters per second, we need to run the wind tunnel at about
28 meters per second, which is well within its capability,” Wilkinson
added. “The tests generally have shown the smoother the fabric, the
lower the drag.”

Speedo International’s research and
development team, Aqualab, took those results and used them to help
create a new swimsuit the company says is its most hydro-dynamically
advanced to date.

Video of Speedo fabric testing will be
available on the NASA Television Video File. For downlink and
scheduling information and links to streaming video, visit:

For more information about NASA and agency programs, visit:


– end –

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