Lecture by John F. Brady

Department of Chemical Engineering, California Institute of Technology

The Micromechanics of Complex Fluids

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 (12K JPG)

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 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.

Previous BSL Lecturers

• 2001-'02
  William R. Schowalter
  University of Illinois
• 2002-'03
  Klavs F. Jensen
  Massachusetts Institute of Technology

Transport Phenomena:
A Landmark in Chemical Engineering Education

As the chemical engineering profession developed in the first half of the 20th century, the concept of "unit operations" arose as the natural organizing principle in educating chemical engineers. Particularly in undergraduate education, underlying theories of mass, momentum and energy transfer were presented only to the extent necessary for a narrow range of applications. Following World War II, chemical engineers moved into a number of new areas in which problem definitions and solutions required a deeper knowledge of the fundamentals of transport phenomena than those provided in the textbooks on unit operations.

In the 1950's, R. Byron Bird, Warren E. Stewart, and Edwin N. Lightfoot stepped forward to develop an undergraduate course at the University of Wisconsin to integrate the teaching of fluid flow, heat transfer, and diffusion. From this beginning, they prepared the landmark textbook, Transport Phenomena, published in 1960 by John Wiley & Sons.

This textbook, referred to by generations of chemical engineers simply as BSL after its authors, would remain in print for 41 years and see five translations. BSL has changed fundamentally the organizing principle in virtually all chemical engineering curricula worldwide. The enduring strength of BSL is testimony to the vision and attention to detail of its authors.

In "retirement," the three authors found time to thoroughly revise BSL, the second edition of which appeared in the summer of 2001. With new or revised discussions of such topics as two-phase systems, angular momentum, Taylor dispersion and turbulence, the revision promises to help prepare students well into the 21st century. The BSL Lecture was inaugurated in the fall of 2001 to honor the achievements of these outstanding chemical engineers.