Obituary: Stephen H. Davis

By Geoffrey B. McFadden and Richard J. Braun

Stephen Howard Davis, the Walter P. Murphy Professor Emeritus of Engineering Sciences and Applied Mathematics at Northwestern University, passed away on November 12, 2021, at the age of 82. Steve was a renowned applied mathematician who specialized in fluid mechanics and materials science, and he conducted a broad and productive research program that made important contributions to the theory of hydrodynamic stability [3], interfacial phenomena [4], and multiscale analysis [7, 12].

Steve was born in New York City in 1939. When he was three years old, his family moved from Brooklyn to Long Beach, NY. His father Harry was a dental mechanic and cabinet maker, and his mother Eva was a classically trained concert pianist who also taught music; all of his grandparents were originally from Kiev and had fled to the U.S. to escape Russian pogroms. Steve attended a small public school in Long Beach from kindergarten through 12th grade. He enrolled in Rensselaer Polytechnic Institute (RPI) at the age of 16 and earned his bachelor’s degree in electrical engineering in 1960. He then remained at RPI to complete his M.S. and Ph.D. in mathematics under the direction of Lee Segel, graduating in 1964 with a dissertation about the theory of free surface and boundary effects on Bénard convection [2].

Immediately after receiving his Ph.D., Steve spent two years at the Rand Corporation in southern California. During this time, he met and married Suellen (nee Lewis), the love of his life. Steve then held a lectureship at Imperial College London from 1966-1968 before joining the Mechanics Department at Johns Hopkins University. While there, he rose through the academic ranks as an assistant professor (1968-1970), associate professor (1970-1975), and full professor of mechanics and materials science as well as earth and planetary science (1975-1978). In 1979, Steve left Johns Hopkins for the Department of Engineering Science and Applied Mathematics (ESAM) at Northwestern University, where he also held joint appointments in the Department of Mechanical Engineering and the Department of Chemical and Biological Engineering. Together with his close colleague Bernard Matkowsky, Steve helped establish ESAM as a leading center of applied mathematics in the U.S. It continues to serve as a mecca for students, postdocs, faculty, and visiting researchers.

Steve possessed an encyclopedic knowledge of bifurcations and stability in mechanics and was a master of asymptotic expansions for the generation of approximate solutions to differential equations. For example, he specialized in the use of long wave asymptotics to derive simplified evolution equations for complicated models, including lubrication theory for thin films [12]. A representative example of Steve’s work is his fundamental advances to the theory of contact line dynamics [9, 10]. He also made essential contributions to the theory of interfaces and phase boundaries [4, 13], especially with the inclusion of nonlinear and non-equilibrium effects at free boundaries in hydrodynamics and materials science. Steve was a pioneer in the study of flow-interface interactions [5, 8] and produced many highly cited review articles about various applications of the theories. 

Beyond his talent for research itself, Steve made many other important contributions to the research community. He guided the submission and review procedures for several NASA research programs for nearly 30 years, thus helping to train a generation of scientists and engineers to thoughtfully evaluate and address proposals. Steve was twice elected chairman of the American Physical Society’s (APS) Division of Fluid Dynamics (DFD) and held additional offices in the DFD. He was a member of the SIAM Council in the 1980s and sat on committees for the National Academy of Sciences, National Academy of Engineering, and U.S. National Committee on Theoretical and Applied Mechanics.

Steve routinely gave back to the applied mathematics community in other ways as well. He served as an editor of the Journal of Fluid Mechanics—the field’s flagship journal—for over 40 years, including 10 years as the main editor (2000-2010). In addition, he was editor of the Annual Review of Fluid Mechanics, SIAM’s “Monographs on Mathematical Modeling and Computation,” Cambridge University Press’ “Monographs on Mechanics,” and the Proceedings of the Royal Society of London. Steve mentored 40 Ph.D. students, many of whom have since established their own distinguished careers in academia and industry; all benefitted from his remarkable taste in research topics and interdisciplinary collaboration. Steve produced over 250 publications in top journals, with more than 20,000 citations in Google Scholar. He was an excellent verbal and written communicator and authored several influential texts and technical monographs, including a book that summarized his work on solidification theory in materials science [6]. He was also in high demand as a plenary lecturer at national and international conferences and held visiting positions at top universities in the U.S., Europe, and Australia. 

Steve’s distinguished awards include APS’s Fluid Dynamics Prize and the Society of Engineering Science’s G.I. Taylor Medal. A collection of research papers dedicated to Steve in commemoration of his 60th birthday was published in 2002 [1], and a special issue of the Journal of Fluid Mechanics appeared in 2010 in honor of his 70th birthday. This volume contains a personal reflection on Steve’s career by G. Paul Neitzel [11]. Furthermore, ESAM at Northwestern University recently established an annual lecture in Steve’s name.

Throughout his career, Steve was an outsized presence at the annual meeting of the APS DFD — which always featured several presentations by Steve and his students and collaborators. A social focus of this event was his organization of an informal conference dinner, where free-wheeling—not to say well-lubricated—discussions of conference highlights usually took place. The introduction of sessions about hydrodynamic applications in materials science, which combined several of Steve’s research interests, serves as another example of Steve’s impact at the conference.

Steve and Suellen provided a warm cultural and social home to their dozens of academic children. In his spare time, Steve was an avid bridge player and an accomplished sportsman who played basketball and tennis at a high level.

Steve had a remarkably deep and lasting impact on his many colleagues around the world, all of whom have benefitted greatly from his personal charm, wit, charisma, and gift for research.

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References
[1] Canright, D., McFadden, G.B., Miksis, M.J., Neitzel, G.P., & Smith, M.K. (2002). Interfaces for the 21st century: New directions in fluid mechanics and materials science. London, England: Imperial College Press, London.
[2] Davis, S.H. (1976). Convection in a box: Linear theory. J. Fluid Mech., 30(3), 465-478.
[3] Davis, S.H. (1976). The stability of time-periodic flows. Ann. Rev. Fluid Mech., 8, 57-74.
[4] Davis, S.H. (1987). Thermocapillary instabilities. Ann. Rev. Fluid Mech., 19, 403-435.
[5] Davis, S.H. (1990). Hydrodynamic interactions in directional solidification. J. Fluid Mech., 212, 241-262.
[6] Davis, S.H. (2001). Theory of solidification. In Cambridge monographs on mechanics. New York, NY: Cambridge University Press.
[7] Davis, S.H. (2017). The importance of being thin. J. Engineer. Math., 105(1), 3-30.
[8] Davis, S.H., Muller, U., & Dietsche, C. (1984). Pattern selection in single-component systems coupling Bénard convection and solidification. J. Fluid Mech., 144, 133-151.
[9] Dussan V, E.B., & Davis, S.H. (1974). On the motion of a fluid interface along a solid surface. J. Fluid Mech., 65(1), 71-95.
[10] Miksis, M.J., & Davis, S.H. (1994). Slip over rough and coated surfaces. J. Fluid Mech., 273, 125-139.
[11] Neitzel, G.P. (2010). Stephen H. Davis – 70, and counting. J. Fluid Mech., 647, 3-12.
[12] Oron, A., Davis, S.H., & Bankoff, S.G. (1997). Long-scale evolution of thin liquid films. Rev. Mod. Phys., 69(3), 931-980.
[13] Spencer, B.J., Voorhees, P.W., & Davis, S.H. (1991). Morphological instability in epitaxially strained dislocation-free solid films. Phys. Rev. Lett., 67(26), 3696-3699.

Geoffrey B. McFadden is a NIST Fellow Emeritus in the Applied and Computational Mathematics Division at the National Institute of Standards and Technology. Richard J. Braun is a professor of mathematics in the Department of Mathematical Sciences at the University of Delaware.