Title: Granular flow near the jamming transition

Author (Invited): Gregg Lois, Yale University

Abstract:

Granular media play an important role in many diverse natural and technological settings, including the motion of earthquake faults, the transport and handling of pharmaceutical or chemical products, and the formation of planetesimals. To better understand these phenomena it is necessary to study how collections of grains respond to external stresses that, depending on various parameters, can cause the material to flow or respond elastically. A great deal of progress has been made in this direction: at low densities extensions of kinetic theory have been developed and make accurate predictions; at very high densities granular media are well described using approaches from elasticity theory. The challenge is to bridge the gap and unravel the behavior at intermediate densities where the system transitions from an inertial response to an elastic response. Indeed, this is often the critical density range when considering catastrophic events in earthquakes, landslides, and hoppers. I will review a recent theoretical approach that relies on the existence of large length scales near the jamming transition to model granular flow at intermediate densities. In addition to motivating new experimental measurements, this approach suggests a degree of universality in granular flows near jamming.