April 23, 2002

Fighting Cavities

Computational Fluid Dynamics chart
Jeff Shaeffer

Who knew bubbles were bad? Cavitation is the formation of bubbles, or cavities, caused when the pressure against a surface under water is lower than the pressure of water vapor. Cavitation is problematic because it causes glass, concrete, and metal to deteriorate. Experiments to simulate it are costly, so Dennis Bieryla (mechanical engineering) is testing a computer model — a computational fluid dynamics numeric code that models cavitation. Based on a study with a wedge in a water tunnel, he simulated cavity size by determining the percentage of water flow that was in the vapor phase. The computer model does not replace experiments, Bieryla explains, but it reduces their number by pre-testing their design.

—Elizabeth Jin

A Sticky Situation

Jar of clover honey on short, white, three-legged stand with casters
Stephanie E. Palumbo

Honey seems harmless, but it can contain a dangerous bacterium called Clostridium botulinum. By age two, humans are immune to the bacterium's spores. But infants can contract botulism, a life-threatening disease characterized by muscle paralysis. Sara Hillegas (environmental systems engineering) explored methods for inactivating the dangerous spores. She inoculated honey with C. sporogenes, a similar bacterium, then exposed it to pulsed UV light in different combinations of treatment time, honey depth, and distance between the light source and the honey. Hillegas reduced the number of spores by almost 90 percent when she placed a shallow pan of honey about 3 inches from a pulsed UV lamp for 45 seconds.

—Bridget Gleeson

Fractal of the Cost

Young man with van dyke wearing a blue shirt with white stripe. Left arm resting on counter.
Adrienne Gammiere

Talking on your cellular phone, do you have to yell to be heard? The cell towers are also yelling, but the phones can hardly hear. The small antennas on the phones can't receive very low frequencies and are incredibly energy inefficient due to their size, so the towers must be extremely large to send messages to the phones. Joshua Petko (electrical engineering) is using the mathematical concept of fractals to design better antennas of the same size. Fractals are repeating patterns, such as tree branches. Petko found that "denser tree shapes make better tree fractal antennas."

—Hadley Rose

Last Updated April 23, 2002