Award to Support Research that Parallels that of Gibbs - Over a Century Later

Professors Corey O’Hern and Jerzy Blawzdziewicz from the Departments of Mechanical Engineering and Physics will receive funding from the National Science Foundation's Division of Chemical, Bioengineering, Environmental, and Transport Systems (CBET) to determine the fundamental physical principles that govern the behavior of jammed and slowly flowing granular materials—frictional particles that range in size from millimeters to centimeters and beyond, including everything from pharmaceutical powders to soils.
While granular materials can mimic simple gases and liquids when they are vibrated, sheared, or otherwise driven (as shown in the movie below), their properties cannot be characterized by the same fundamental laws, which relate temperature, pressure, and volume. In contrast to fluids, the correct set of variables to use when describing the state of the system is not even known.
The Yale researchers, in collaboration with experimentalist Prof. Mark Shattuck from the Department of Physics and Benjamin Levich Institute at CCNY, will work to identify the macroscopic variables that characterize granular systems with the goal of developing a new formulation of statistical mechanics that would provide a predictive understanding of the properties of these nonequilibrium systems.
While it is likely that in the long run this work will lead to improvements in the efficiency of packing, mixing, or conveying of granular materials or other applications not yet imagined, like much in scientific discovery, O’Hern states that we must understand the fundamental aspects of granular media independent of the practical aspects. “While I would like to make an impact in the practical world immediately, I cannot start to do that if I do not even know what equations to use to describe these systems,” says O’Hern. “We are really in the dark in this area.”
This work by Mechanical Engineering Professors O’Hern and Blawzdziewicz to formulate a statistical mechanics for granular materials and other nonequilibrium systems parallels that of Yale Professor Josiah Willard Gibbs (Ph.D., Yale Engineering, 1863), who first developed the field of equilibrium statistical mechanics more than a century earlier.

Movie from experiments in which seven millimeter glass beads are vibrated and allowed to come to rest. Afterward, low-amplitude, high-frequency vibrations are applied until the system relaxes. This process is repeated many times in subsequent experiments. Can we predict the frequency with which different types of packings (with different arrangements of grains) occur?