Numbers paint the picture




The destruction of southern Louisiana by flood water is a thing of beauty. Not in reality, of course; that would be a terrible calamity. But on Joannes Westerink’s computer screen it appears as graceful swirls of red, yellow and blue undulating in a green sea, morphing over time across a map of the coast. The image, which could be abstract art, is in fact an animated graph of what would happen to the Louisiana coastline from a hurricane-generated storm surge. The undulating colors signify the depth of the flow, increasing from yellow to red.

“You can see this 10- to 16-foot wave shoot up the Mississippi River,” the Notre Dame associate professor of civil engineering says. “That’s the level of detail we can get with this computer model,” which is perhaps one of the best tools to minimize the effects of such a natural disaster.

The image was created by an artist named AdCirc, an abbreviation for Advanced Circulation model, a complex computer program developed by Westerink and colleagues at the University of North Carolina —Chapel Hill to “solve equations of motion for a moving fluid on a rotating earth.” The software, which is still being refined after 16 years, can be used to solve a variety of engineering problems, including flood-control design, pollution spread and silt.

At the core of AdCirc is an analytical technique more commonly used in structural engineering than in the study of fluids. “With this we can convert partial differential equations, which mathematicians can’t solve, into algebraic equations that can be solved, and that allows us to analyze coastal flooding problems with a very high degree of resolution,” Westerink explains.

Besides being used by Louisiana State University researchers to predict the effect of hurricane storm surge, AdCirc has been used by the U.S. Army Corps of Engineers to help design levees for flood control along the Mississippi River. The newest version of the software makes 7.5 million calculations every two seconds to create accurate graphic animation of water flow.

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