WobLog

Catching up on old magazines, I caught an article in the August 2008 issue of Physics Today on the physics behind Speedo's LZR Racer swimsuits, which made such a big "splash" at the 2008 Olympics:

Competition in the pool at this month's Beijing Olympics will be not only among world-class swimmers but also their swimsuits. Since its debut in February, the low-drag hydrophobic Fastskin LZR Racer swimsuit from Speedo International Ltd has had more than 44 world records broken in it; critics allege that the $600 "space-age" suit, in part developed by NASA scientists, gives its wearers an unfair boost in buoyancy and amounts to "technological doping." The company claims a 5% decrease in drag over the previous model but no buoyancy increase, and the suit, along with competing models, has been approved for Olympic competition by FINA, the international swimming federation.

The LZR Racer is a descendant of the full-body swimsuit Speedo introduced in 2000 to mimic the viscous-drag-reducing denticles on a shark's skin. The shark suit proved that surface-engineered synthetic materials can be made to have lower drag than a swimmer's shaved skin. The next move for Speedo's internal R&D unit was to form a team of external partners led by Barry Bixler, the late Honeywell Corp engineer and computational fluid dynamics (CFD) expert, to further cut the passive drag.

[...]

"There is still debate as to what the primary source of drag is for a shark, but for a swimmer, it is primarily form drag," says Amy Lang, an experimental fluid dynamicist at the University of Alabama. From CFD simulations and studies in a swimming flume, the researchers determined that total drag is reduced when low-drag polyurethane panels are inserted to compress the chest, upper thighs, and other areas of the swimmer's body where form drag is most pronounced. "We spent a lot of time [on the previous model] drag testing anatomically accurate mannequins" in the flume, says David Pease, a biomechanist at the University of Otago in New Zealand. "This time around involved quite a bit more actual athlete testing in order to test differences in compression and support provided by the new suit."

The article goes on to describe some of the work going on in preparation for the 2012 Olympics, extending research from minimizing drag during the glide phase of a stroke to include combating drag during the active phase of each stroke.