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Professor’s simulations used for storm models

Karen Langley | Monday, September 12, 2005

Since Hurricane Katrina struck the southeastern United States two weeks ago, Notre Dame students have joined audiences around the globe in prayer and fundraising for the storm’s victims – but most students are unaware that a member of the Notre Dame faculty is deeply involved in efforts to prevent future storms from causing such destruction.

For more than 15 years, professor Joannes Westerink of the department of civil engineering and geological sciences has developed the ocean circulation models that allow engineers to design structures dependent on water conditions, such as New Orleans’ system of levees.

“We have been working with the Corps of Engineers New Orleans District for eight years,” Westerink said. “Everyone in southern Louisiana is using the model.”

The New Orleans District used the software of the Advanced Circulation Model (ADCIRC) to design the city’s levees. After Hurricane Betsy caused massive destruction in 1965, the engineers decided to update their models.

The software provides information to engineers so they know how structures will react to storms of different intensities, Westerink said.

“The major problem is that it requires funding from the government, and that has not been coming,” he said. “It’s about the risk they are willing to take. The design storms were Category 3. There have been quite a few Category 3 storms, and the levees held.”

While the government does fund the current research needed to protect the city from hurricanes, Westerink said increased funding is necessary.

The engineering costs to provide protection from a Category 5 storm would be $2.5 billion, he said. In the context of engineering, this is not an extraordinary cost. A major bridge costs $1 billion to construct, and the Big Dig in Boston will require $11 billion, Westerink said.

“You can see how the storm has taken lives, which of course are irreplaceable, and will now cost hundreds of billions of dollars in reconstruction,” he said. “And that doesn’t even account for the economic fallout.”

The software models measure how fast water flows, how high it flows and where and when it will flow. There are also components that track the flow of pollution and sediment.

Westerink came up with the ADCIRC with Rick Luettich, his roommate during their first year of graduate studies at MIT and now a professor at the University of North Carolina, Chapel Hill. The pair has actively worked on the model’s development since completing graduate school more than 15 years ago.

“As is true with any successful partnership, the collaborators need to have complementary roles,” Luettich said. “Dr. Westerink has often been the visionary, daring to propose extremely challenging modeling feats.”

This boldness can be exemplified by the efforts in southern Louisiana, Luettich said.

“The complexity of representing flow structures at scales of meters in the context of processes extending over hundreds of kilometers is monumental,” he said. “Dr. Westerink has doggedly pursued this application and should be widely recognized for his efforts.”

To design the model needed for these simulations, the scientists and engineers working in Westerink’s Computational Hydraulics Lab must use applied mathematics, computer science, coastal oceanography and engineering.

The model relies on the principles of conservation of mass and conservation of momentum, which are formulated into differential equations to describe the physics of a situation.

“The heart of the model changes differential equations to algebraic equations that can be solved by computers,” Westerink said.

The mathematics involved in the ADCIRC models are so complicated that the calculations for one storm require 128 to 512 computer processors working simultaneously.

“We work on the biggest Department of Defense supercomputers,” he said. “Such intensive calculations would take months to do on one computer.”

While the public’s attention is now focused on the southeastern region of the United States, the ADCIRC model is applicable to any region. It is currently used in simulations for the Persian Gulf, the Mediterranean and the East and West coasts of America.

When reconstruction of New Orleans starts, Westerink’s models will once again be employed to give engineers a better understanding of the natural forces they will face.

“It’s human nature to learn from our mistakes,” he said. “And sometimes it takes a tragedy for us to make our engineered systems safer.”