Going for the goo

Professor Ed Cussler and a team of intrepid swimmers take the plunge for science in an unorthodox experiment

by judy woodward

The lean-muscled swimmer stands poised at the side of the pool, glances a bit apprehensively into its depths, and then dives quickly into the greenish, slimy liquid. A few gelatinous globules bob gently to the surface.

What has happened to the normally azure, chlorine-scented waters of the University Aquatic Center?

Much as the scene resembles the anxiety-fueled dream of an athlete the night before a big swim meet, the swimmer and pool actually were part of a real-world—though admittedly unconventional—foray into experimental fluid mechanics.

For a few hours last summer, a University pool was transformed into a body of water that looked more like a fully functioning swamp than a swimmer's arena. Members of the University swim team became field researchers in an effort to settle one of the questions that has intrigued scientists—and swimmers—for centuries:

What effect does the viscosity of a fluid medium have on the speed of a body traveling through it?

Imagine the sensation of swimming through maple syrup. Would you move faster or more slowly than you would in ordinary water? Most people assume intuitively that the sticky stuff would slow you down. But what about the possibility that higher viscosity might actually give you a forward boost in the same way a stiff rope ladder allows a climber to ascend faster than a limp one?

For some people, the thought of diving into anything but unadulterated water is the stuff of nightmares, but aquatic center director Duane Proell says that every dedicated swimmer has wondered about the answers to these questions.

Nobody had ever investigated the matter scientifically, though, until chemical engineering professor Ed Cussler and senior Brian Gettelfinger took the plunge.

Last summer, Cussler, Proell, and representatives of groups ranging from the NCAA to campus facilities management—not to mention a band of intrepid swimmers—cooperated to find the answer to a truly sticky problem.

Cussler first speculated about the influence of drag forces on a swimming body more than 30 years ago when he was teaching at Carnegie Mellon University in Pittsburgh. "A rather tubby Uruguayan grad student challenged me to a swimming race," he explains. To Cussler's surprise, she beat him.

The unexpected defeat sparked his interest in the physics of swimming. Then he read an intriguing book by the late Jim Counsilman, a legendary Olympics coach who built the University of Indiana into a swimming powerhouse.

"In The New Science of Swimming Counsilman [talks about] the 'theoretical square law,' which states that 'resistance [to a swimmer's motion] varies with the square of his velocity,'" explains Cussler. "In other words, to go twice as fast [a swimmer] has to pull four times as hard. That just jumped out at me when I read his book."

First proposed by Dutch scientist Christiaan Huygens in the 17th century, the idea that resistance is dependent on the square of the velocity of a moving body has an important secondary implication. It suggests that when it comes to determining the rate of speed, the viscosity (or thickness) of a medium is less important than other factors, like the shape of the body moving through it.

In other words, it matters not how thick the goo, the swimmer's force will pull him through—unless, of course, the goo actually provides an unexpected boost.

Cussler had been thinking about these questions for many years, although he's quick to acknowledge there's no commercial application for his experiment. He points out that he was careful to fund the test out of consulting monies that were not assigned to other research goals.

In the end, it was scientific curiosity, pure and simple, that inspired him to propose an experiment involving an otherwise underused swimming pool in late August.

Gettelfinger was an eager collaborator. In addition to his studies in chemical engineering, he's also a varsity swimmer.

"Anyone who's swum extensively has been curious about what it would be like to swim in something other than water," he says. "[The question] crossed my mind a couple of times, but I thought a test couldn't be done."

Gettelfinger was able to persuade several of his fellow swimmers to donate a summer's day to the pursuit of scientific research. "The other swimmers are mostly English majors," he reports. "They just [thought] it [was] funny."

Before they could dive into their work, so to speak, several layers of University administration had to approve the project. "Everything we've done has required the cooperation of a lot of people," says Cussler. "The aquatic center authorities, the people from hazardous materials, facilities management—all had to agree to it." Even the NCAA got involved because the swim team needed a waiver for the highly irregular session.

Proell admits he was slightly taken aback when he first heard Cussler's proposal to dump 700 pounds of guar gum, a thickening agent, into one of the University's pools. Fortunately, though, he recognized the proposal's educational merits.

"Cussler is persuasive, but we didn't need much persuading. We all agreed that we had an opportunity here to be part of the University's educational mission. [The experiment] involved movement through water. [I]n aquatics, that's our business. It intrigued us."

After securing the necessary permissions, the researchers grappled with the problem of transforming a swimming pool into the working equivalent of a giant bowl of maple syrup. Normally found in products like ice cream and shampoo, guar gum in its natural state is a gritty off-white powder; however, when added to liquid, it tends to clump into telltale globs unless blended vigorously.

According to chemical engineering junior Jonathan DeRocher, the researchers discarded their initial plan for mixing the guar with water. "We were standing around when we saw a garbage can. Our first idea was to mix it in batches and dump them over the side into the swimming pool. Then [chemical engineering adjunct professor] Jeff Schott said we could do it continuously with a pump mechanism."

The team devised a Rube Goldberg-like contraption using a large green plastic garbage can, a drill with a mixing head, and a length of PVC piping. The device permitted them to pump the guar gum solution directly into the pool, an operation that took about four hours on a Saturday afternoon.

On the following Monday the swimmers assembled at the pool, which had been closed to outsiders for the experiment. Only one preliminary step remained: Someone had to test the waters.

In the best tradition of a commanding officer who doesn't expect troops to follow where he will not lead, Cussler made the first leap into the guar-laced pool. Although the greenish cast of its waters suggested a rich profusion of pond scum, Cussler emerged showing no ill effects. The experiment was ready to begin.

During its first stage, swim team members and other volunteers swam timed laps in the guar pool. They used a variety of strokes and also tested swim fins and drag suits. After showering and resting, they repeated the process in a nearby "control" pool filled with ordinary chlorinated water.

Volunteer Eric Nuxoll, a postdoctoral associate in chemical engineering, equated the sensation to "swimming through Tang" and estimated the guar pool to be about two-and-a-half times as thick as normal water. Cussler's calculations later put the ratio at about twice the viscosity of water.

"This was the most oddball experiment I've ever done,' says DeRocher. "I've learned that Professor Cussler has very original ideas. Some work, some don't."

The findings of this unorthodox investigation?

Swimming in "syrup" doesn't really make that much difference one way or another, according to Cussler. "Swimming in guar does not change swimming speed," he says. "The standard deviation between lengths for competitive swimmers is 2.4 percent, the same as that recorded by their coaches in normal workouts."

Not that the experiment didn't come up with other interesting findings. Cussler also had been interested in the relationship between fluid mechanics and the swimmer's physique.

"The best swimmers should have the body of a snake and the arms of a gorilla," he concludes. "The fact that elite swimmers are not all shaped like this is a wonderful reminder that fluid mechanics is not the only factor in swimming fast."