Stephen H. Davis

Stephen H. Davis, Walter P. Murphy Professor Emeritus of Engineering Sciences and Applied Mathematics at Northwestern University, passed away on 12 November 2021, following complications from cardiac bypass surgery. He was 82 years old.

Steve was born in New York City on 7 September 1939. He and his family moved to the city of Long Beach on Long Island when he was 3 years old. Although he was accepted to study in nearby New York City, Steve elected to move upstate, entering Rensselaer Polytechnic Institute (RPI) at age 16. He took his bachelor’s degree in electrical engineering but then pursued MS and doctoral degrees in applied mathematics. Applied mathematics at RPI was a storied department in that era, with a heavy emphasis on continuum mechanics, given the presence on the faculty of Dick DiPrima, George Handelman, and Lee Segel, among others. Steve’s dissertation research was done under Segel and was entitled, “The effect of property variations and surface curvature on Bénard convection.” Surface effects remained an area of interest for Steve for his entire career. In addition to receiving an excellent education at RPI, he adopted several of its traditions—notably, a lack of academic stuffiness that he carried with him throughout his career and life.

Steve’s first position following RPI was one he held from 1964-66 at the Rand Corporation in Santa Monica, California. While at Rand he met and married Suellen Lewis of Dallas. Over the course of their 56 years together, Suellen became known nearly as well as Steve throughout the fluid dynamics community. After a brief lectureship in the mathematics department at Imperial College, London (1966-68), Steve accepted a position in the Department of Mechanics at the Johns Hopkins University, where he remained until January 1979, when he moved to Northwestern.

It was at Johns Hopkins where Steve established his presence in the fluid dynamics community among colleagues such as Owen Phillips, Kim Parker, Bill Schwarz, and, especially, Stanley Corrsin; Steve established his reputation as both an outstanding researcher and excellent teacher. A tradition of daily 10:00am coffee in a room adjacent to what is now known as the Corrsin Wind Tunnel had Stan and Steve presiding over a collection of faculty, students, visitors, and staff—all addressing one another on a first-name basis. Conversations ranged from science to politics, sports, and humor, creating a collegiality unmatched in other academic departments. At Northwestern, his open-door policy and willingness to meet and discuss any topic (especially his beloved New York Yankees) established a relaxed and friendly atmosphere in the department. When visiting his office for the first time, one was introduced to experimental photographs that provided the spark for much of his theoretical work. There was always a constant flow of internationally renowned visitors attracted to the department because of Steve’s presence. Wherever he went, he built a collegial community.

Steve’s renown as a researcher in the field of fluid dynamics was for pioneering work on contact-line dynamics, the stability of time-dependent flows, flows in thin films, including rupture, and the stability of flows driven by temperature-induced surface-tension variations. Later in his career, he became interested in problems in materials science, particularly those in which flow processes played a role. He was a worldwide leader in the dynamics of crystal growth, with contributions to rapid solidification, anisotropic-material effects, mushy-zone convection, and nonlinear evolution of cellular growth. His unique ability to apply mathematics to important problems in materials science is captured in his 2001 monograph, Theory of Solidification, published by Cambridge University Press.

Steve was recognized for his work through election to the National Academy of Engineering (1994), the American Academy of Arts and Sciences (1995), the National Academy of Sciences (2004), and Academia Europaea (2017). He was the 1994 recipient of the APS Fluid Dynamics Prize and was awarded the 2001 G. I. Taylor Medal of the Society of Engineering Science. He was also a recipient of the Humboldt Prize in the 1980s.

Those accolades, however, do not begin to encompass Steve’s impact on his fields of study, nor do they do justice to his well-known personality. As a professor, his courses were always very popular because he delivered complicated material in a clear, understandable way. As an adviser to his graduate and postdoctoral students, Steve was blessed with the ability to suggest relevant, timely problems, being able to see the end from the beginning, and knowing that the proposed topic would yield important results. When a research student encountered the inevitable brick wall, he was able to suggest a workaround that ultimately led to the problem’s successful completion.

Steve’s influence on fluid mechanics worldwide cannot be overstated, and many consider him to have been one of the foremost fluid dynamicists in the world in his time. A two-time chair of the APS Division of Fluid Dynamics, he was also the editor of the Journal of Fluid Mechanics (JFM) and Annual Review of Fluid Mechanics, the first to hold this joint appointment. His service on the editorial board of JFM spanned more than 40 years, and he served as the first, and to this day only, non-Cambridge editor of the journal. Although his office was sparsely appointed, he had a complete collection of JFM on his walls and one would frequently find him sitting in his office reading the current issue.

Steve is survived by his wife, Suellen, a brother, Jeffrey, and an academic family consisting of scores of former graduate students and postdoctoral fellows. To his many friends who did not understand the complexities of his work, Steve will always be remembered for his warm consideration of others, his ever-engaging sense of humor, and his love of travel and fine dining. Whether you were a lawyer, a physician, an engineer, or were just engaging him in a conversation about any aspect of life, Steve had a joke to fit the situation. He will be missed by all who knew him.