Biography
Professor Kozlowski's lab aims to address fundamental questions of flow and clogging in granular materials, collections of grains like rocks, coffee beans, sand, or pills. With experimental lab techniques, he and his students capture and model the motion of grains under gravity-driven flow from silos, containers with an opening at the bottom. Moreover, using an experimental technique called photoelasticimetry, the forces between individual grains can be surmised in order to develop a complete physical description of the motion and mechanical interactions of grains during pouring. The current focus of the lab is on the flow rate, flow direction, clogging probability, and clogging arch formation in the vicinity of the silo opening in systems with different boundary geometries and grain shapes (such as idealized circular grains and more realistic angular polygonal grains).
Granular materials are one kind of system under the umbrella of "soft matter systems," which include such materials as foams, gels, biological tissue, liquid crystals, and emulsions. Grains are especially challenging to understand using basic theoretical physics models because, unlike these other systems, grains are "athermal," meaning they do not have inherent fluctuations due to thermal energy modes, and grains in nature are "dissipative," meaning that collisions and sliding action between grains dissipates kinetic energy. Yet understanding granular materials' bulk behaviors -- the ways in which these systems can behave similarly to, but not the same as, conventional solids, liquids, and gases -- is vital in a large number of societal applications, especially agriculture and pharmaceuticals. Moreover, the challenge for physicists to develop a unifying description of granular materials across phases is at once difficult and enticing, and will surely keep us busy for quite some time!