Bridging the Spatial and Temporal Scales in Dense Granular Systems Description of Dense Granular Shear Flows

Kondic

DMS-0605857

The project centers on analyzing and understanding the

nature of information propagation through dense granular systems.

The properties of the signals are then used to deduce the basic

physical mechanisms of the force and energy transmission. These

mechanisms have been the subject of considerable study lately

because it is crucial to understand whether the forces between

granular particles propagate in a manner that can be described

under an elliptic, hyperbolic, or parabolic framework. The

starting point of this project is development of large scale

discrete element simulations that are used to analyze response of

dense granular systems to space- and time-dependent

perturbations. The results of the simulations are then employed

to help formulate effective models for bridging the scales

between micro (grain scale) and meso (hundreds or thousands of

grains) descriptions of granular systems. Both static and

dynamic granular systems are considered, making it possible to

analyze the interplay between granular dynamics and signal

propagation. This setup also allows for considering some

important features of dense granular flows, such as the role of

force anisotropy and underlying microstructure. The project is

carried out in close collaboration with experimental work

performed at Duke University.

Dense granular systems are one of the most challenging

systems in the field of soft condensed matter, in particular

because they are subject to jamming, and fall in between solid

and liquid states of matter. Analysis of signal propagation

through these systems allows us to understand how granularity on

a micro scale influences macroscale behavior. The novel research

techniques used here also can be applied to other soft condensed

matter systems that experience jamming, such as emulsions,

colloids, gels, and foams. In addition, signal propagation

through granular systems is of considerable importance in a

number of practical problems including oil recovery,

vibrofluidized beds, and some important humanitarian efforts,

such as detection of land mines. The project addresses basic

issues in statics and dynamics of dense granular systems;

understanding of these basic concepts allows for future progress

in developing better models needed for numerous applications of

granular materials.