Steven Alan Orszag, a pioneer in applied and computational mathematics whose work had a deep influence in the field of fluid mechanics, died May 1. He was 68 years old.
The Percey F. Smith Professor of Mathematics at Yale, Orszag specialized in fluid dynamics, especially turbulence; computational physics and mathematics; electronic chip manufacturing; computer storage system design; and other topics in scientific computing. His work included the development of spectral methods, pseudo-spectral methods, direct numerical simulations, renormalization group methods for turbulence and very-large-eddy simulations.
In the areas of computational fluid dynamics, he achieved the first successful computer simulations of three-dimensional turbulent flows. He also developed methods that provide a fundamental theory of turbulence. Another of Orszag's primary research interests was the development of techniques for the simulation of electronic chip manufacturing processes, some of which have been applied extensively throughout the industry.
"Steve was a pioneer in applied and computational mathematics high-performance computing and more recently novel approaches to mathematics education," said John Wettlaufer, the A.M. Bateman Professor of Geophysics & Physics and professor of applied mathematics at Yale. "Vast areas of the landscape of thought have lost a brilliant thinker and a wise adviser."
Orszag's accomplishments in the area of spectral methods include the introduction of fast surface harmonic transform methods for global weather forecasting and filtering techniques for shock wave problems.
"The intrinsic difficulty of using such methods in nonlinear problems was known to fluid dynamicists and this was a major impediment to progress until Steve developed the transform methods that still form the core of many large-scale spectral computations," Wettlaufer said. "Understanding both the mathematics and the computational challenges of implementing them formed an enormous part of Steve's career and influence."
Orszag was the founder of and/or chief scientific adviser to a number of companies, including Flow Research, Ibrix (now part of HPQ), Vector Technologies and Exa Corp. He was awarded six patents and wrote over 400 archival papers.
He was the author, with Carl M. Bender, of "Advanced Mathematical Methods for Scientists and Engineers: Asymptotic Methods and Perturbation Theory," a standard text on mathematical methods for scientists. Other books he co-wrote or co-edited include "Studies in Applied Mathematics," "Numerical Analysis of Spectral Methods," "Supercomputers and Fluid Dynamics," "Japanese Supercomputing: Architecture, Algorithms, and Applications" and "Large Eddy Simulation of Complex Engineering and Geophysical Flows."
He served as chief editor or series editor of the Journal of Scientific Computing, the Springer Series in Computational Physics, and the American Institute of Physics Series on Computational and Mathematical Physics.
Orszag's research contributions have been widely recognized. He was awarded the American Institute of Aeronautics and Astronautics Fluids and Plasmadynamics Prize in 1986. He was a John Simon Guggenheim Fellow in 1989, and won the Otto Laporte Award of the American Physical Society in 1991 and the G. I. Taylor Medal of the Society of Engineering Science in 1995. He has been named an ISI Highly Cited Author by the ISI Web of Knowledge.
Before joining the Yale faculty, Orszag was the Forrest E. Hamrick Professor of Engineering at Princeton University (1984-1998) and professor of applied mathematics at MIT (1967-1984). He received his B.S. in mathematics from MIT at age 19 and his Ph.D. from Princeton in Astrophysics, which he completed in three years, and was a member of the Institute for Advanced Study.
Orszag, who was born in New York City, is survived by his wife of 47 years, Reba; his son Michael; his son Jonathan and his wife Rica; his son Peter Orszag and his wife Bianna Golodryga; his grandchildren Leila and Joshua Orszag; and his sister Myrna Baron.