Jan. 18, 2002 NEW BRUNSWICK/PISCATAWAY, N.J. – Wind shear, the force feared by airline pilots, has an important earthbound counterpart, write Rutgers engineers in a paper published Jan. 17 in the prestigious science journal "Nature." Benjamin J. Glasser and Troy Shinbrot found that when multiple streams of granular material flow together – whether the materials are debris in a landslide or powders used in manufacturing – the multiple streams can suddenly take on a wavy flow that mimics action seen in liquids or gases.
Shinbrot is an associate research professor and Glasser is an assistant professor and associate director of the pharmaceutical engineering program in Rutgers department of chemical and biochemical engineering. They worked with David J. Goldfarb, now at the Schering-Plough Research Institute, on the paper entitled "Shear instabilities in granular flows."
The discovery has a wide range of implications in areas ranging from pharmaceutical manufacturing to predicting how landslides will behave, the scientists said.
"At some point, almost all pharmaceutical tablet production relies on granular materials or powders flowing down chutes," said Shinbrot, who studied computer videos of materials streams working themselves into virtual whitecaps. "Understanding how and why the materials interact as they flow can lead to more consistent pharmaceutical products."
The average pharmaceutical tablet weighs only a quarter of a gram, and Glasser noted that each may include only a few milligrams of active ingredient. "Variation in the mixture because of shear forces during manufacture can lead to a pill not doing what it's supposed to do," he said. "It can be dangerous." The use of flowing granular material is also common in other industries such as food manufacturing and mining.
Formulas developed over the years for understanding how flowing liquids and gases create shear activity have led to more accurate weather forecasting, safer air travel and more-efficient ships. He said the discovery of shear instability in granular flows could potentially lead to development of equations and formulas for flow of granular materials.
Shinbrot and Glasser said one of the more dramatic applications of granular flow research may be in understanding landslides. "In time we may be able to predict where and how landslide debris will flow. This could help us do a better job of warning people and placing barriers where they'll do the most good," Glasser said.
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