Patterns and collective behavior in granular media: Theoretical concepts

Abstract

Granular materials are ubiquitous in our daily lives. While they have been a subject of intensive engineering research for centuries, in the last decade granular matter attracted significant attention of physicists. Yet despite a major efforts by many groups, the theoretical description of granular systems remains largely a plethora of different, often contradicting concepts and approaches. Authors give an overview of various theoretical models emerged in the physics of granular matter, with the focus on the onset of collective behavior and pattern formation. Their aim is two-fold: to identify general principles common for granular systems and other complex non-equilibrium systems, and to elucidate important distinctions between collective behavior in granular and continuum pattern-forming systems.

Thermal properties of an impurity immersed in a granular gas of rough hard spheres

“…Moreover, the activity of this research field has grown enormously over the last decades [4][5][6][7], becoming an important area of study in the field of soft matter physics [8,9]. In particular, the control of granular dynamics has a large impact on a variety of industries, including some high-technology related interesting studies [10][11][12].…”

“…However, several important experimental features of granular collisions can only be captured with a more elaborate collisional model [35]. In particular, particle spin (i.e., the grains angular velocities) can have an important role in the global properties of the granular gas dynamics [7], see Fig. 1.…”

Experimental Evidence of a Rayleigh-Plateau Instability in Free Falling Granular Jets

“…Such jets start out spatially uniform and breakup into clusters farther downstream as may happen for ordinary liquids under the action of surface tension forces. This is surprising since attractive forces between grains (at the heart of capillarity in liquids [3]) are much weaker than other mechanical forces at play (gravity, friction, inelasticity) [4,5]. Such a clustering instability has been observed for free falling granular jets in air, in quiescent liquid baths, and in vacuum [6][7][8][9].…”

Experimental Observation of Modulation Instability and Optical Spatial Soliton Arrays in Soft Condensed Matter

“…In particular, continuum models have previously been of great utility in understanding the pattern forming properties of granular media [21]. MI in nonlinear systems may also lead to more complex pattern formation, such as two-dimensional square lattices, hexagonal and spiral type formation; this may be achieved by driving the system well above the threshold [21].…”