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Don Ho's got nothing on George Karniadakis and
Martin Maxey, applied mathematics professors at
Brown University. While the crooner sings of "Tiny
Bubbles," Karniadakis and Maxey are immersing
themselves in microbubbles. These yet-tinier bubbles,
about 50 to 500 microns in size, can cut ships'
drag, reduce the amount of fuel ships use, and
increase ships' range.
For 30 years, microbubble systems
have been studied experimentally. Pistons push
air through porous plates representing a ship’s
hull and into tanks of moving water. Researchers
have moved the locations of the plates. They've
increased and decreased the number and size of
the bubbles. And they've seen an incredible change
in drag--reductions of as much as 80 percent.
But they haven't been able to figure
out what the optimal microbubble system looks
like--where to insert bubbles, how many to insert,
and how big to make them. To develop the optimal
system, they must understand the fundamental physics
of water's flow around the hull and the microbubbles'
impact on that flow. Microbubbles foil traditional
methods of measuring the flow details in an experimental
tank because optical systems can't see through
the Alka-Seltzer fizz created by the bubbles.
To get around that problem, Karniadakis
and Maxey are creating the first first-principles
computational models of microbubbles in action.
"Most of the people involved in studying
microbubbles, even today, are experimentalists.
We're doing the only direct numerical simulations
of microbubbles in turbulent flows," says
Karniadakis, who has used NCSA resources since the late 1980s.
By shifting his team's microbubble
research to NCSA's newest Itanium-processor-based
Linux cluster, called Titan, Karniadakis improved
the state of the art by a factor of forty--jumping
from models that track a mere 500 bubbles to models
that track about 20,000 microbubbles. 
Access Online | Posted 2-11-2003
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