CDI-Type II: Collaborative Research: Computational Homology, Jamming, and Force Chains in Dense Granular Flows

This project will employ a highly interdisciplinary approach that integrates new geometrical techniques, modeling, and experiments to address fundamental, open questions concerning the physical properties of granular media and other jammed materials such as glasses, foams, and colloids. The hallmark of jammed materials is that they resist applied forces like solids, but are disordered like liquids. In addition, many jammed materials possess heterogeneous, ramified structures known as force chain networks when external forces are applied. Although the existence of force chains has been known for decades, a quantitative understanding of their role in physical processes has proved elusive in part because previous studies have been unable to devise an unbiased and general definition for them. Precise identification and characterization of force chains and the response of jammed materials to applied forces will likely have a transformative impact in many arenas. For example, financial and energy costs of handling and processing of granular materials, typically with high inefficiency, is estimated to be at least one trillion dollars in the US alone. Also, avalanches and earthquakes are examples where the unpredictable behavior of granular media detrimentally impacts mankind. In this work, we will apply novel mathematical techniques coupled with computer simulations and experiments to obtain a quantitative, predictive description of jammed materials. The outreach efforts of this project emphasize providing educational opportunities to students from underrepresented groups. We will organize education and recruiting trips to predominantly female liberal arts colleges in the Northeast and historically black schools in North Carolina, such as North Carolina Central University, and others in the Southeast. These trips will include giving technical and popular lectures, including demonstrations to show that research on jammed materials is intriguing and important. During informal meetings with students we will emphasize that careers in science and technology are rewarding and open to those in underrepresented groups. To stimulate further student interest in this research, we will hold biannual 2-day lab open houses so that promising undergraduates can be exposed to both experimental and theoretical aspects of our research. To encourage close collaboration among researchers in the field of jammed materials, we will organize biannual interdisciplinary workshops. The inaugural workshop, ``Computational Homology Tools Applied to Jamming and Flow in Granular Materials'' is scheduled for the winter of 2009.