The Dynamics of Granular Flows
Jerry Gollub
Haverford College and University of Pennsylvania
How can we best describe
materials composed of particles that flow like
fluids, like sand, powders, or the sediments found in geophysical
settings? We normally
describe fluids by partial differential equations,
but the possibility of doing so reliably for granular systems is still
unclear. I will discuss studies of the anomalous behavior of granular
materials that illustrate their unique properties compared to other
condensed matter systems. For example, when sheared, random granular
matter can crystallize, dramatically affecting its flow properties. In
some cases both ordered and disordered states coexist, with the
disordered state being metastable. These and other experiments raise
interesting questions about how prior history is recorded in the
internal
structure of granular packings, affecting their instantaneous rheology.
Additional puzzling issues include: The role of polydispersity,
anisotropy, and chirality; the onset of stick-slip motion and its
connection to fracture; the behavior of internal stress networks during
time-dependent flows; and the statistics of fluctuations in granular
systems.
Jerry P. Gollub,
Professor in the Natural Sciences (Physics)
Physics Department,
Haverford College
370 Lancaster Avenue
Haverford, PA 19041
USA
http://www.haverford.edu/physics-astro/Gollub/