Granular Materials

Sand making an interesting patternStrolling on the beach we notice that our feet create dry spots around them. The sand around the leopard’s feet flows while it speeds along the desert. Close to the ocean, we often notice dark striations on the sand. These phenomena are so familiar to us that we hardly ever pause to wonder about their origin. The surprising fact is that we do not really understand why sand behaves the way it does. In the world of granular materials, gravity is far more significant than temperature. We observe granular materials all around us, but have yet to gain a solid understanding of their behavior. 

For the last five years Prof. Chakraborty has been working on developing a theory of granular materials that can predict their collective behavior. The puzzling nature of granular materials is portrayed in this NSF-produced video that followed the Nature paper on shear-jamming by the Chakraborty-Behringer collaboration. Recent work has focused on constructing a statistical ensemble for granular solids, the nature of jamming in hopper flows and the origin of rigidity in dry granular solids.

Hopper Flows

Things flow out of hopper. But when hoppers get clogged it is problematic. Our research investigates how to get things flowing again.

Investigating Researcher: Carl Merrigan

Discontinuous Shear Thickening

When you pump a fluid it tends to get thicker as you pump harder. Sometimes it only takes a very slight push for a thin liquid to become very thick. 

Investigating Researcher: Jetin Thomas

Granular Networks

Modeling packings of grains reveals that contact networks govern the behavior of the grains.

Investigating Researchers: Kabir Ramola, Edwin Faican

Plastic Failure

Some materials yield if you push them beyond a certain point. We look at the statistics of these plastic failures to gain insight into this phenomenon.

Investigating Researcher: Jishnu Nampoothiri

Active Matter

Active matter is comprised of agents, each of which consume energy to produce motion. These types of systems can be seen all around us: from flocks of birds, to the collective motion of bacteria, to the intracellular transport of materials.

Active Networks

Cells use active networks — biological filaments and motors — to transport things around the cell. At Brandeis we study a simplified system with only one type of filament and motor. This system exhibits several interesting rheological properties as well as spontaneous flow. We study a computational model of this system.

Investigating Researcher: Daniel Goldstein