The Physics of Sand

Granular Materials

Strolling 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 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 important and temperature is not. This is stuff that we see around all around us but know very little about. 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 except for when they don't. Hoppers getting clogged can be a real problem, we look into how to get things flowing again.

Investigating Researcher

Discontinuous Shear Thickening

When you start to pump a fluid it can get thicker when you try and pump it harder. Sometime it goes from not very thick to very thick with only a bit of a push. 

Investigating Researcher


Granular Networks?

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

Investigating Researches

Plastic Failure

Some materials yield if you push them too much. We look at the statistics of these plastic failures to gain insight into them. 

Investigating Researcher

  • Jishnu Nampoothiri

Active Matter

Active matter is comprised of agents, each of which consume energy to produce motion. These types of system 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