A “renaissance man” of rheology

Ronald Larson’s pioneering work on fluid mechanical instabilities led to his election to the National Academy of Engineering in 2003. His groundbreaking discovery that a new class of instabilities in polymers was due to elasticity rather than inertia, helped advance the understanding of fluid dynamics and rheology, the study of the flow of matter. Additionally, his extensive collaboration within Bell Labs solved complex problems critical to industry, a testament to how academic research can apply scientific discoveries to real-world application

For elucidating the flow properties of complex fluids at the molecular and continuum levels through theory and experiment: View the NAE citation.

Affiliations

• Professor, Mechanical Engineering
• Professor, Chemical Engineering
• Professor, Macromolecular Science & Engineering
• George Granger Brown Professor of Chemical Engineering
• A H White Distinguished University Professor of Chemical Engineering

Background & education

• Professor, Chemical Engineering, University of Michigan,1996
• Ph.D., Chemical Engineering, University of Minnesota, 1980
• M.S., Chemical Engineering, University of Minnesota, 1977
• B.S., Chemical Engineering, University of Minnesota, 1975

In their own words

Tell us a little about yourself

Larson: “I’m passionate about understanding things, just in general. I see phenomena and I like to understand them. I like being confronted with mysteries. I describe it to my students as a process that I call “creative confusion”: it’s when you’re most creative, when you’re confused, and you know there has to be an answer in there, but you can’t quite see it.

“I grew up in Northern Minnesota. I’d get up at 5:30 in the morning and get out on my bike with big balloon tires and deliver newspapers like a lot of people growing up around there. Then I had the good fortune to get a scholarship that would allow me to go to the University of Minnesota. I picked chemical engineering as a balance between my love of chemistry and my desire to get a job and be practical. I assumed I would stop at a bachelor’s degree like my father had, but I got into research as an undergrad, thanks to a professor there that asked me to do a project for him in the summer and I loved it.”

Can you share a Eureka moment, or a turning point?

Larson: “I remember when I found it and it was very exciting. We had the first of a new kind of class of instabilities that occur with polymers due to a phenomenon of elasticity rather than what normally causes these, which is inertia. I did many things at Bell Labs, but that was probably the thing that just suddenly was like something we knew was really big right at the start.”

“If you’re rotating a cylinder inside another cylinder with fluid in it, the fluid would go round and round, and if you go fast enough, it will form these rolls and will start to form bands. We saw the same thing except the cylinder was barely moving and we knew it was so slow, it couldn’t possibly be this instability.

“We found that it was due to the elasticity of the molecules. The molecules were stretching out and they were creating a totally new kind of instability called the galactic instability. We had to come up with an explanation because it was not anything that had been seen before. And it came down to just working with these equations and looking for something called the naked function and eigenvalue.

What advice would you give an engineering student?

Larson: “Ask questions, slow down and think through issues. I’ve noticed that the ratio of thought to word has gone way down. Back when you had quill pens, people thought hard before they wrote any word, and now you don’t have to think at all because we have chatGPT and you can type any question and you’ll get as many words as you want without ever thinking about any of it.

“I teach fluid mechanics, so I decided to see if chatGPT could explain how you throw a curveball in baseball. So I asked about that and when I took it to the class and we looked at the answer, it got it wrong. But it sounded right. Everything sounded right. You could read it quickly and it looks absolutely right. But if you think about it and sketch it out and look at it carefully, it has it wrong. That’s what you can do with a facile use of words just sounding good and not being thoroughly thought through, challenged where somebody challenges the assumptions and you talk about and discuss it.”

---

Quotes edited from interview transcript between Ronald Larson and Marcin Szczcepanski.