The Micromechanics of Complex Fluids

Lecture by John F. Brady

Department of Chemical Engineering
California Institute of Technology

Thursday, April 8, 2004
Room 1800 Engineering Hall
Lecture at 4:00 p.m.
Refreshments at 3:45 p.m.

It's morning. You pour cereal in your bowl, shake the orange juice, fill your glass, and pour milk over your cereal. Why did you shake the orange juice and not the milk? Why do you pour cereal?

These are just some everyday examples of complex fluids — materials that often behave like water or air, but just as often display quite different behavior. Many complex fluids are in the form of particles dispersed in a host liquid or gas, and it is the particle-level interactions that give rise to interesting macroscopic phenomena, such as shear thinning and thickening, viscoelasticity and structure formation. This talk will discuss the micromechanics of particulate dispersions and how the interplay of colloidal, Brownian and hydrodynamic forces set the material's microstructure and determine its macroscopic properties. Examples of hard-sphere systems ranging in size from a few nanometers, where Brownian motion is important, to larger sand-grain-size mixtures will be investigated computationally, analytically and experimentally.

So why did you shake the orange juice and not the milk?

John F. Brady

John F. Brady is the Chevron Professor of Chemical Engineering at the California Institute of Technology. He received his BS in chemical engineering from the University of Pennsylvania in 1975 and spent the next year at Cambridge University as a Churchill Scholar. He received both an MS and PhD in chemical engineering from Stanford University, the latter in 1981. Following a postdoctoral year in Paris at the Ecole Superiéure de Physique et de Chimie Industrielles, he joined the Chemical Engineering department at MIT. Dr. Brady moved to Caltech in 1985, where he has remained ever since, serving as department chairman from 1993-1999.

Dr. Brady's research interests are in the mechanical and transport properties of two-phase materials, especially complex fluids such as biological liquids, colloid dispersions, suspensions, porous media, etc. His research takes a multilevel approach and combines elements of statistical and continuum mechanics to understand how macroscopic behavior emerges from microscale physics. He is particularly noted for the invention of the Stokesian Dynamics technique for simulating the behavior of particles dispersed in a viscous fluid under a wide range of conditions.

Dr. Brady has been recognized for his work by several awards, including a Presidential Young Investigator Award, a Camille and Henry Dreyfus Teacher-Scholar Award, the ASEE Curtis W. McGraw Research Award, the Corrsin and Batchelor lectureships in fluid mechanics, and the Professional Progress Award of the American Institute of Chemical Engineers. He has held positions as the Juliot-Curie Professor at ESPCI and the J.M. Burgers Professor at Twente University, and currently has a part-time Chair in Applied Physics at Twente University in the Netherlands. Dr. Brady has been an associate editor of the Journal of Fluid Mechanics since 1990. He is a fellow of the American Physical Society and a member of the National Academy of Engineering.