Research That's Truly Explosive
With funding from the Department of Energy, a team of researchers from WPI will spend the next five to 10 years creating computer simulations of fires and explosions. The team, led by Homer Walker, head of the Mathematical Sciences Department, is part of a group of American mathematicians and scientists working on similar research.

Along with Walker, Marcus Sarkis, assistant professor of mathematical sciences at WPI, and Michael Tocci '92, a mathematical sciences research associate, are collaborating with their counterparts at the University of Utah's Center for Simulation of Accidental Fires and Explosions (C-SAFE). Walker was a mathematics professor at Utah State University and a member of the C-SAFE team before he came to WPI in 1997.

The DOE established C-SAFE with a five-year, $26.8 million contract through its Accelerated Strategic Computing Initiative (ASCI), a program designed to improve the safety and security of the nation's nuclear stockpile. The agency also funded similar centers at Caltech, Stanford, the University of Chicago and the University of Illinois at Urbana-Champaign. (None of the work at these university centers is classified or involves nuclear weapons.)

"The overall goal of C-SAFE is to develop an integrated problem-solving environment that will effectively exploit the power of massively parallel computers to carry out 'full-physics' simulation of fire scenarios involving hydrocarbon liquids, chemical explosives, containers and other structures," Walker says. "At WPI, we will focus on developing numerical algorithms and software to solve extremely large problems--ultimately involving billions of equations and unknowns. We will use a new generation of massively parallel computers, the most powerful in the world, which have been installed at the national laboratories."

Possible scenarios that may be investigated on these computers include a fire at an explosives manufacturing plant or the crash of an airplane carrying explosives. "The simulations will be based on 'first principles' of physics and chemistry that model fuel combustion, the coupled flow of combusting gases above the fuel, the transport of heat and the ultimate combustion of the materials, among other factors," Walker says.

A high-performance parallel computer will make possible the complex computations. Funding for the computer has been provided by a $145,000 grant from the National Science Foundation, with additional support from United Technologies Corp. and WPI research funds.

"This machine will be a major computing resource for this and many other research and educational activities in the Mathematical Sciences Department and elsewhere on campus," says Walker. "With our project-oriented undergraduate curriculum and our department's emphasis on applied and industrial mathematics and statistics, it will provide many unique opportunities for combining research and education to students at all levels."

DOE funding through C-SAFE supports the researchers, each of whom brings impressive credentials to his work. Walker earned a B.A. in mathematics at Rice University and an M.S. and Ph.D. at New York University's Courant Institute of Mathematical Sciences. Before coming to WPI, he was a faculty member at Texas Tech University, the University of Houston and Utah State University, and held visiting faculty positions at the University of Denver, Cornell University, the University of New Mexico and Yale University.

Sarkis, an expert on numerical algorithms for parallel computing and computational fluid dynamics, also earned a doctorate at the Courant Institute. He spent four years as a postdoctoral associate at the University of Colorado at Boulder before joining the WPI faculty in 1998. Tocci majored in math at WPI and completed his Ph.D. at North Carolina State University in 1997.

The software and numerical algorithms Walker, Sarkis and Tocci expect to develop may also find applications in other research under way in the Mathematical Sciences Department. In addition, members of the University of Utah's C-SAFE team have begun to formulate strategies for integrating their research results into the undergraduate engineering and science curriculum.

"Courses based on the work of the ASCI team may also be incorporated into the WPI undergraduate curriculum within the next few years," Walker says. "Because of our affiliation with C-SAFE, we would be among a very few American universities to offer this experience. As a department, we're involved in many applications that are really important to the rest of science, engineering and society. We try to seize every opportunity to involve our students in these activities."

Where the Rubber Meets the Road
The United States Air Force is interested in Robert Lipton. The low-key mathematical sciences professor isn't being groomed to be a pilot or fly a space mission, but his research is important enough for the Air Force Office of Scientific Research (AFOSR) to have supported it with two grants totaling more than $100,000 since 1996.

In his research, Lipton is studying the effect of the interfaces where the components of composite materials meet. The goal is to see how these interfaces affect the overall structural, electrical and thermal properties of the composite.

In composites, two or more materials are blended or combined to form a distinct product. Examples include steel-belted tires, steel-reinforced concrete, the laminated materials used in modern composite airplane wings, and thermal apparel designed to withstand heat, cold or moisture. Lipton has developed new theoretical methods that can be used to relate the nature of the bonds that form between a material's constituent components and the properties of the resulting composite. He recently gave an invited talk on the effects of interfaces in concrete at the 13th Mechanics Division meeting of the American Society of Civil Engineers.

"Composite materials and their transport properties are central to the design of structures for uses ranging from molecular sieve catalysis to ceramic thermal barrier coatings," says Lipton. "The intent of the research is to provide a rigorous theoretical baseline from which we can derive practical rules of thumb for the design of composite materials."

If Lipton is successful, his work could lead to substantial savings for the Air Force and manufacturers in a number of industries. Scientists and researchers seeking better, stronger or more heat-resistant products would be able to select materials based, in part, on how the bonds between them would affect the physical properties of the finished composite product.

The recent DOD/Air Force contract expands research on interfaces that Lipton has been conducting for several years. In previous studies, he focused on particle- or fiber-reinforced materials used in electronic packaging. The challenge for research and development teams is to create packaging materials that can efficiently transport heat away from electronic devices.

Lipton has developed a mathematically rigorous method to identify particle dimensions and shapes that most effectively reduce the thermal energy dissipated inside a particle-reinforced composite package.

"It's very enjoyable to use mathematics to 'tease out' underlying physical properties that often lie behind simply stated mathematical models," Lipton says.

Lipton earned a B.S. in electrical engineering/computer science at the University of Colorado and M.S. and Ph.D. degrees in mathematics at New York University's Courant Institute of Mathematical Sciences. Prior to joining the WPI faculty in 1990, he was the Charles B. Morrey Assistant Professor of Mathematics at the University of California, Berkeley, a postdoctoral fellow at Cornell University's Mathematical Sciences Institute, and a process engineer at United Technologies in Colorado Springs, Colo.

-Bonnie Gelbwasser