John F. Brady

John F. Brady

California Institute of Technology

1954 – Present

Chemical Engineer
Awarded Bingham Medal 2007
Fellow, Elected 2015

John F. Brady was born in Dunkirk, New York on January 8, 1954. He graduated in 1975 from the University of Pennsylvania with a B.S. in Chemical Engineering and, after spending a year at Cambridge University as a Winston Churchill Scholar, entered the Chemical Engineering graduate program at Stanford University from where he received an M.S. in 1977, followed by a PhD three-and-a-half years later. His PhD thesis, under the supervision of Andy Acrivos, was entitled “Inertial Effects in Closed Cavity Flows and their Influence on Drop Breakup” and dealt with the application of asymptotic analysis to the solution of several fundamental problems in viscous flow theory. Following a year as an NSF-CNRS US-France Exchange Scientist (1980 to 1981), which he spent at the Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI) directed by P-G. de Gennes, Brady joined the Chemical Engineering department at the Massachusetts Institute of Technology as an Assistant Professor. In 1985, he was lured away by Caltech where he has been ever since; first as an Associate Professor (1985 to 1989) and then as Professor of Chemical Engineering (1989 to present). He also served as the Executive Officer of Chemical Engineering at Caltech (1993 to 1999 and again 2013-2019) and was a holder of a part-time Chair in Applied Physics at the University of Twente in the Netherlands (2002 to 2006). He has held the Chevron Professorship of Chemical Engineering since 1999 and is also a Professor of Mechanical Engineering (since 2005).

John is known internationally for his seminal and wide-ranging contributions to the study of complex fluids including suspensions, emulsions, colloidal dispersions, ceramics, liquid crystals, ferrofluids, electro- and magneto-rheological fluids. Three of John’s numerous achievements stand out. The first was the creation and development (together with his French collaborator Georges Bossis) of Stokesian Dynamics (SD) — a molecular-dynamics-like method for predicting the microstructural and macroscopic properties of c omplex fluids. Prior to SD, theoretical studies of suspensions, which had steadily progressed since the original work of Einstein, had reached an impasse owing to the impossibility of dealing numerically with the complexities of the many-particle interactions. The creation of SD, however, radically changed this by providing a computational avenue to the study of the dynamics of dense disperse systems which compliments the traditional approaches of analytical theory and laboratory experiment. Thus, SD ushered in a new era of investigation, not only for suspensions but for multiphase flows generally, in that it allowed one to rigorously solve many long-standing problems and, more profoundly, to pose new questions. Also, a remarkable feature of SD is the spectrum of physical forces (hydrodynamic, electrostatic, colloidal, Brownian, etc.) and the range of both length and time scales (tens of angstroms to centimeters, and microseconds to days) encompassed by one technique.

SD has yielded quantitative a priori predictions of suspension behavior that are in excellent agreement with experiments for a variety of systems, ranging from the structure, diffusion and rheology of colloidal dispersions, to yield stresses in electro-rheological fluids, and finally to the self-induced concentration inhomogeneities in pressure-driven flows. More fundamentally, new insights into microstructured fluid behavior, such as the profound importance of cluster formation, have emerged from such simulations. Ultimately, the understanding brought about by simulating the relationship between the microstructure and macroscopic properties of suspensions will enable the design and engineering of novel materials to meet desired applications. These advances have been achieved not only by John himself but by numerous other investigators using John’s SD code, which he has generously and selflessly shared, for the asking, over the years.

The second major contribution of John’s in complex fluids is his development of a scaling theory for the diffusive and rheological behavior of concentrated colloidal dispersions. Specifically, he has shown, in a series of papers, how the most important effects of hydrodynamics can be included by a simple rescaling of the time or the shear rate by the concentration-dependent self-diffusivity. This observation has led to quantitative a priori predictions of the divergent behavior of the suspension viscosity at high solids concentrations, thereby explaining experimental observations spanning a period of over 50 years. This theory also suggests a universal scaling for the rheological behavior of any suspension of non-attractive particles. This scaling has also been demonstrated experimentally and can be used to correlate a vast array of rheological responses displayed by colloids.

His third landmark contribution in suspension rheology was the development (with P. Nott) of the so-called suspension balance model to serve as a constitutive equation for the macroscopic description of such systems. Some years earlier, Leighton & Acrivos, motivated by an idea originally due to Ascher Shapiro as well as by observations from Francis Gadala-Maria, proposed a so-called trajectory model of shear induced particle diffusion which, was heuristically able to account for a number of puzzling experimental results such as the shear-induced re-suspension of heavy particles. In spite of its initial success, however, the trajectory model was found to suffer from a number of shortcomings. For example, it predicted that particles would migrate if the suspension was sheared in a parallel plate device but not in a cone and plate apparatus, whereas experiments showed that the reverse was the case. Also, it could not account for the normal stress differences which Gadala-Maria had measured some years earlier. Finally, it was far from clear how the trajectory model could be extended beyond any but the simplest unidirectional flows. In contrast, John & Nott’s suspension balance model is based on the principles of mechanics plus dimensional analysis and, as modified subsequently by Jeff Morris, not only avoids the shortcomings of the original trajectory model, but can also serve as a proper constitutive equation for a large class of complicated, and even some three-dimensional, flows. Consequently, it is the suspension balance model which is currently used on a worldwide basis when studying the flow behavior of concentrated suspensions.

John has received numerous international awards including the AIChE Professional Progress Award (1998), and has been elected to the National Academy of Engineering (1999), the American Academy of Arts and Sciences (2014), and most recently the National Academy of Sciences (2020). In addition, he served as an Associate Editor of the Journal of Fluid Mechanics (1990 to 2004) and became the Editor of the Journal of Rheology in July 2005. And last but not least, he has proven to be an outstanding mentor of Ph.D. students, a number of whom, e.g. Don Koch at Cornell, Ron Phillips at the University of California at Davis, Louis Durlofsky at Stanford, Roger Bonnecaze at the Univ. of Texas at Austin, Jeff Morris at the Levich Institute CCNY, Aditya Khair (CMU), Ubaldo Córdova-Figueroa (U.Puerto Rico-Mayaguez), Roseanna Zia (Stanford), Jim Swan (MIT), and Sho Takatori (UCSB) are rapidly developing international reputations of their own.


“Brady, John F.” American Men and Women of Science, 29th ed.; Gale: Farmington Hills, MI, 2011; Vol. 1.

John F. Brady. Division of Chemistry and Chemical Engineering, Caltech (accessed Aug 7, 2020).

Caltech Faculty Elected to the American Academy of Arts and Sciences. Caltech, News - April 28, 2014 (accessed Jul 31, 2019).

Note: This biography is an adaptation of the following article previously published by The Society of Rheology.

Brady to Receive 2007 Bingham Medal. Rheology Bulletin 2007, 76(2).