PHILIP A. THOMPSON (1928-2001)

BY ROGER SCHMIDT, JOSEPH SHEPHERD, AND
CLAUDIA THOMPSON

PHILIP ANDREW THOMPSON made significant contributions to thermodynamics and fluid dynamics throughout his career as both a scientist and an educator. His decades of research — from his doctoral studies and academic investigations to his tenure as a professor at Rensselaer Polytechnic Institute (RPI) in Troy, New York, and later collaborations with colleagues at the Max Planck Institute für Strömungsforschung in Germany — led to fundamental advancements in understanding compressible flow and the behavior of real fluids across the full range of thermodynamic states, including phase change. A lifelong learner with an ever-curious mind, he also had a great love for the land, the outdoors, and woodworking. He passed away on March 23, 2001, in Troy, at the age of 72.

Born on Sept. 10, 1928, in Galesburg, Illinois, Philip was the son of Wallace and Cornelia Anne (Simpson) Thompson, who were both highly influential figures. His father was a widely respected constitutional authority and Illinois Senate majority leader, while his mother was a much-admired leader in the community who ran for the Senate seat formerly held by her husband following his unexpected passing at the age of 56.

In 1946, Philip married his high school sweetheart, Norma Jean Ruttgen, and served in the United States Army from 1946 to 1948. After his military service, he worked as a plant engineer at Albany International in upstate New York (1952-57) and later at Dynatech in Cambridge, Massachusetts (1957). He earned his bachelor’s and master’s degrees in mechanical engineering from RPI in 1957 and 1959, respectively. Awarded a National Science Foundation fellowship, he continued his graduate studies at the Massachusetts Institute of Technology, where he earned his Ph.D. in 1961 working under renowned fluid mechanics researcher and educator Ascher Shapiro (NAE 1974).

During this period, Philip and Jean purchased a 100-acre property in rural Berlin, New York, where they settled with their growing family — Philip Andrew Jr., Stephen, Claudia, and Bruce. Philip undertook major renovations to an old farmhouse and property and managed the land as a tree farm as an avocation. Professionally, Philip joined the faculty at RPI in 1960, where he taught for more than three decades until he retired as professor emeritus in 1993. A highly respected professor, he challenged, supported, and inspired his students, serving as a mentor to many.

In addition to his teaching and academic work, he held numerous research positions in industry and government. He served as a research engineer at the David Taylor Model Basin in Portsmouth, Virginia (1961); a research engineer at Boeing in Seattle (1962); and a fluid mechanics researcher at General Electric in Schenectady, New York (1964-65). He also consulted for Watervliet Arsenal (1968-69) and Lone Star Industries (1970-72). From 1978 to 1979, he was a program manager for the Division of Energy Storage Systems at the U.S. Department of Energy in Washington, D.C., overseeing the development of techniques for using compressed air in pumped hydro energy storage.

In 1975, Philip was the recipient of the Alexander von Humboldt Research Award from the Federal Republic of Germany, after which he took a sabbatical from RPI to serve as a visiting scientist at the Max Planck Institute für Strömungsforschung in Göttingen, Germany. His appointment at the institute was then extended through 1978. Subsequently, he continued his research and work with colleagues there on projects in 1981, 1988, and 1989.

Philip was the author of Compressible Fluid Dynamics, originally published by McGraw-Hill in 1972 as part of its Advanced Engineering Series. This treatise has served generations of physicists and engineers and remains a vital resource for instructors, students, and researchers. In addition, he published numerous scientific articles. An outstanding researcher in experimental fluid dynamics, as well as a strong theoretician and respected teacher, Philip had a special interest in thermodynamics and compressible flow, which he explored extensively with his students and collaborators. His research emphasized the importance of thermodynamic state and real fluid properties in compressible flow phenomena such as nozzle flows, shock, and expansion waves. He also devised innovative experimental methods, earning international recognition for the uniqueness and excellence of his work. His contributions to fluid dynamics provided significant insights with important technological applications.

Philip was among the first to realize the significance of the fundamental gas dynamic derivative and the unexpected behavior that arises when it takes unusual values. Single-phase fluids exhibiting negative or sign-changing fundamental derivatives are now referred to as Bethe-Zel’dovich-Thompson (BZT) fluids, honoring the contributions of Philip alongside earlier researchers. Rejecting the classical approaches to compressible flow based on ideal gases, he devoted the remainder of his career to exploring the compressible flow of real fluids — liquids, gases, and multiphase mixtures — integrating thermodynamics with compressible fluid motion equations to investigate a wide range of complex phenomena. Generations of researchers have benefited from his elegant exposition of the fundamental derivative’s role, particularly in his 1971 Physics of Fluids paper.¹ One of his most groundbreaking findings² was the possibility of rarefaction shock wave, previously thought to be impossible in gases. Philip and his students demonstrated that these shocks could occur near the critical point, opening up an area of research that remains active today.

A particularly significant aspect of his real fluid studies involved the retrograde behavior of organic fluids with large specific heats. His theoretical predictions³ and experimental demonstrations revealed surprising behavior, including fluids that condensed on experiencing a shock. One of Philip’s major scientific achievements was his demonstration of the richness of compressible flow with phase changes, exemplified by his prediction and experimental demonstration of new phenomena such as partial and complete liquefaction shocks,⁴ evaporation fronts resembling deflagration waves, metastable nozzle flows, and condensation shocks with wave splitting.⁵ These discoveries continue to have practical relevance today in the utilization of alternative working fluids in power generation and refrigeration cycles.

Philip’s ceaseless love of teaching, combined with his mischievous sense of humor, is fondly remembered by his children. He frequently gave impromptu lessons on scientific phenomena from their earliest years. His daughter, Claudia, recalled how he demonstrated the creation of bore waves in a stone canal that they had built in their large backyard. He also delighted in illustrating the Doppler effect after a lunchtime discussion on sound frequencies. “He had just bought a new Corvette, a rare luxury that he allowed himself,” Claudia remembered. “He took us down to the end of our dirt road where it met the highway and asked us to listen. After revving up his new sports car and driving by us at a high speed while laying on the horn, we heard the change in pitch from high to low — and we immediately grasped the change of sound frequencies caused by objects coming toward us versus those moving away. Grinning as he wheeled the car back around to our stationary point, he asked, ‘Would you like me to demonstrate that again?!’”

Life on the Thompson Tree Farm involved extensive work in the woods, managing both hardwood and coniferous forests, planting and cultivating trees, and harvesting wood for heating and construction. The family also undertook ambitious building projects, including renovating the house with hand-pegged cherry floors and fine woodwork, as well as constructing a stone barn using fieldstone collected from old mountainside walls. Evenings were often full of indoor and outdoor games, stargazing, and storytelling. Shared canoeing and backpacking trips, along with other adventures, deepened the family’s bond. Later in life, Philip’s exceptional woodworking skills shifted from structural craftsmanship to sculpture.

Philip had a deep appreciation for crafts, art, and science — and the intricate connections between them. A devoted student of history, he also had an immense appreciation for music, literature, and poetry, as well as food and wine. He treasured the time he spent working in Europe, where he built collegial relationships with scientists across the continent. While living and working in Göttingen, he once rode his bicycle 750 kilometers (approximately 470 miles) to Delft, Netherlands, to present a research paper at the IUTAM (International Union of Theoretical and Applied Mechanics) Congress — a solo journey he completed in just over four days.

In addition to his previously mentioned honors, he was elected a fellow of the American Society of Mechanical Engineers in 1984 and was a member of the American Physical Society and the American Association for the Advancement of Science. In 1986, he married his second wife, Nancy Kerls. He was elected to the National Academy of Engineering in 1989 and is listed in Who’s Who in America.

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¹Thompson PA. 1971. A fundamental derivative in gasdynamics. Physics of Fluids 14(9):1843-49.
²Thompson PA, Lambrakis KC. 1973. Negative shock waves. Journal of Fluid Mechanics 60(1):187-208.
³Thompson PA, Sullivan DA. 1975. On the possibility of complete condensation shock waves in retrograde fluids. Journal of Fluid Mechanics 70(4):639-49.
⁴Dettleff G, Thompson PA, Meier GEA, and Speckmann HD. 1979. An experimental study of liquefaction shock waves. Journal of Fluid Mechanics 95(2):279-304.
⁵Thompson PA, Craves H, Meier GEA, Kim Y-G, and Speckmann H-D. 1987. Wave splitting in a fluid of large heat capacity. Journal of Fluid Mechanics 185(December):385-414.