Andreas “Andy” Acrivos, professor emeritus of engineering at Stanford University and an internationally respected educator and researcher who helped transform the field of chemical engineering, especially in the areas of applied mathematics, heat transfer, and fluid mechanics, died Feb. 17, 2025. He was 96 years old.

Acrivos was born and raised in Athens, Greece, where as a teenager he had a passion for history and believed his future lay either as a professional historian or in inheriting his father’s textile business. By the time he graduated from high school, however, he had to abandon those plans.

“The war came, and with it the German occupation,” he told his former student, Eric S.G. Shaqfeh, Stanford’s Lester Levi Carter Professor and professor of chemical engineering and of mechanical engineering, in a 2013 interview. “You can’t imagine how dreadful the occupation was, although we did not suffer as much as an awful lot of other people in Europe. I never thought much about making a living until the war came, and then the equation changed.”

In 1947, with Europe devastated by war, Acrivos accepted a scholarship from Syracuse University to pursue chemical engineering, and together with a classmate made his way to New York aboard a converted troop ship filled with other immigrants. He planned to return to Greece after receiving his bachelor’s degree in 1950, but felt he needed more preparation for a career, so he moved on to the University of Minnesota, where he earned his master’s degree in 1951 and his PhD in 1954. It was there that he became the second graduate student of chemical engineer and applied mathematician Neal Amundson, a mentor who inspired him to become a researcher. In 1954, Acrivos accepted a position as assistant professor of chemical engineering at the University of California, Berkeley, and was promoted to full professor in 1959.

In 1962, Acrivos was recruited to the Stanford Chemical Engineering faculty, where he quickly began to work with Professor David Mason to develop the program, says Shaqfeh.

“When Andy arrived, the department was very nascent; it was an outcropping of the chemistry department with very few faculty and no significant reputation,” Shaqfeh says. “Andy was instrumental in developing the department and putting it on the map. In a very short period, it gained national ranking and international stature, in part because of his presence on the faculty and the strategic decisions he and others made. We consider him one of our founding fathers.”

A fundamental academic, Acrivos focused his research on studying the properties of suspensions, emulsions, and fiber-filled materials. His most notable accomplishments include his work in microhydrodynamics – flows at small scale – a field that was somewhat esoteric at the time, but is now central to lab-on-a-chip technology. Within that subfield of fluid dynamics, he did pioneering work on the boundary integral technique, a numerical method to solve problems in low Reynold’s number hydrodynamics; shear-induced diffusion, a concept with industrial applications and now a standard in all fluid mechanics textbooks; and inclined settling, which involves a way to rapidly settle particles out of liquid.

“In chemical engineering, I think it would be universally agreed that he was responsible for establishing modern-day fluid mechanics principles,” says Gerry Fuller, the Fletcher Jones Professor and professor of chemical engineering in the School of Engineering. “He brought a higher level of mathematical acumen into the transport sciences in chemical engineering, particularly with a process called matched asymptotic expansions, which involves finding different approximate solutions to a very complicated problem, then matching them together to produce an approximate solution that is valid.”

In addition to his research and his success in helping develop Stanford’s Chemical Engineering department, Acrivos is remembered for being a caring but no-nonsense mentor to his students, many of whom went on to remarkable professional success.

Eric Shaqfeh came to Stanford specifically to work with Acrivos.

“At the time it’s fair to say he was the preeminent fluid mechanic in the United States, certainly in chemical engineering,” he says. “He was incredibly demanding with enormously high standards, which he also held for himself as well as his group. He shaped me as a human being and a scientist because of those standards. He taught me how to write – and in some sense how to think – as a scientist. I think all his PhD students feel the same. His real legacy is his students and his academic tree, because all his students begat other students with the same standards.”

Acrivos served as chairman of Stanford’s Chemical Engineering department from 1972 to 1975. In 1988, he took early retirement, gained emeritus status, and accepted the Albert Einstein Chair in Science and Engineering at the City College of the City University of New York, where he served as a professor of chemical engineering and director of the Benjamin Levich Institute for Physico-Chemical Hydrodynamics until his retirement in 2001.

Acrivos also served as the editor of the journal Physics of Fluids from 1982 to 1997, during which time he grew the journal’s fluid mechanics component, radically increasing its influence in that field.

In 2007, he returned to Stanford, where he was associated with the Flow Physics and Computational Engineering Group in the Mechanical Engineering Department.

Acrivos received a wide range of awards and honors in his field, including the National Medal of Science – the nation’s highest award for scientific achievement – for “pioneering research in fluid mechanics, leadership in the fluid mechanics and chemical engineering communities, editorial initiative with the Physics of Fluids, and mentoring several generations of engineering scientists.” He was a member of the National Academy of Sciences, the National Academy of Engineering, and the American Academy of Arts and Sciences. He received the Alan P. Colburn Award from the American Institute of Chemical Engineers (AIChE) in 1963 and the Warren K. Lewis Award from that same organization in 1984. The AIChE Professional Progress award is now named in his honor.

“He was a brilliant man and opened up an intellectual world to his students,” says Shaqfeh. “You could pattern your life by the standards he lived by. His students would always say, ‘What would Andy do?’ and the answer was the smart thing, the right thing, the thing that involved the most scholarship. And he did that over and over again.”

Andreas Acrivos is survived by his wife, Juana, sister Acrivy Stavropoulos, niece Maria and nephew Andreas in Athens, sister-in-law Lily Crespo Vivó and family members Armando and Antonieta Crespo, their children, grandchildren, and godchildren.