The Wake

Mankind has achieved great things with the use of science. Ed Cussler, a professor in the Chemical Engineering department at the University of Minnesota, has achieved great things too. He’s written several books, published over 200 articles, and holds a number of patents in his chosen field. He’s also filled a swimming pool with thickener and tested how it affects swimmers’ speeds. It’s this particular experiment that Cussler will be discussing during the latest edition of Café Scientifique.

Cussler will hold a lecture next Tuesday, October 16, at 7 p.m. at the Bryant Lake Bowl. The event, entitled Experiments in Fluid Mechanics, will focus on the quirky experiment made in August of 2003, when he and Brian Gettelfinger, a chemical engineering senior at the time, wondered how a pool filled with something besides water would affect swimming speed.

“I should point out and reaffirm that this experiment has no practical value whatsoever,” Cussler said with a laugh. “It has no value at all in terms of practice, but it has enormous value in terms of charm.”

When Cussler and Gettelfinger first planned the experiment, they needed a solution they could fill a swimming pool with in order to test the effect on a swimmer’s speed. Cussler originally wanted to fill a pool with corn syrup. Unfortunately, it would have taken an astronomical amount of corn syrup to fill a swimming pool.

“The city of Minneapolis would not let us put that much corn syrup in a swimming pool,” Cussler said. The city worried over how it would be disposed of when the experiment was done. Cussler, with a grin on his face, didn’t know why they were so worried.

“The sewage plant would never run better if we used all that sugar,” he said.

Instead of corn syrup, the scientists decided to use guar instead. Guar gum is an extract from the guar bean, which primarily is found in India and Pakistan. It is a commonly found ingredient in a variety of products, including shampoo, ketchup, and baked goods. According to Cussler, it only took about 700 lbs. of guar to fill the pool.

The scientists recruited 15 swimmers of different swimming abilities to participate in their experiment. The swimmers swam a length of the pool filled with guar, then swam in the pool with water, repeated their length in the pool filled with water, and swam a final length in the pool of guar. Swimming coaches on hand for the experiment directed the swimmers to swim close to the wall, because swimmers close to the wall tend to have slower swimming times. This is why high-seeded swimmers in the Olympics are placed in the center of the swimming pool. Each swimmer’s times were recorded and averaged. What Cussler and Gettelfinger found as a result of this experiment was the guar didn’t affect the swimmers’ speeds.

The reason for this can be explained through Osment Reynolds’ discoveries. Reynolds argued there were two different mechanisms that are present in fluid flow. One is the laminar flow. To the layman, this can be described as a flow in which fluids move through rubbing against each other. This is the flow that happens when a rain drop hits the ground. The second mechanism is turbulent flow, which can be described as pushing away from something, which is exactly what was demonstrated in the pool.

Cussler explained the theory through the use of two grains of sand. The sand, since it is small, is under a laminar limit. If a grain of sand was dropped into a glass of guar gum and a glass of water, the grain of sand inside the guar gum would take twice as long to reach the bottom. However, since humans are bigger, they wouldn’t be affected by the laminar limit, because they are able to push the water as well as the guar away from them. Another demonstration can be used to figure out turbulent flow. By taking several copies of the Wake, taping them together, and trying to run by holding them stretched out, it will become clear that it is difficult to run. However, if the runner holds the copies of the Wake towards the direction where they are running, it becomes much easier to run. Since there’s a smaller area in front of the runner, they can move faster. The viscosity, or resistance in a fluid, of each liquid wouldn’t matter in this case because the swimmers were simply too big to be affected by it. What Cussler and Gettelfinger discovered in this experiment was size as well as velocity mattered when came to figuring out which mechanism is used in fluid movement.

The experiment, while not life-changing, not only drew a large amount of attention but also earned an Ig Nobel prize in Chemistry for both Cussler and Gettelfinger in 2005. The Ig Nobel prize is a parody of the Nobel prize. It is awarded every October to scientists whose quirky experiments not only entertain people, but arouse an interest in science.

The Bryant Lake Bowl is located on 810 West Lake St., in Minneapolis. Admission to the event is $5.