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

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This project will employ a highly interdisciplinary approach that integrates newgeometrical techniques, modeling, and experiments to address fundamental, openquestions concerning the physical properties of granular media and other jammedmaterials such as glasses, foams, and colloids. The hallmark of jammed materials isthat they resist applied forces like solids, but are disordered like liquids. In addition,many jammed materials possess heterogeneous, ramified structures known as forcechain networks when external forces are applied. Although the existence of forcechains has been known for decades, a quantitative understanding of their role inphysical processes has proved elusive in part because previous studies have beenunable to devise an unbiased and general definition for them. Precise identification andcharacterization of force chains and the response of jammed materials to applied forceswill likely have a transformative impact in many arenas. For example, financial andenergy costs of handling and processing of granular materials, typically with highinefficiency, is estimated to be at least one trillion dollars in the US alone. Also,avalanches and earthquakes are examples where the unpredictable behavior ofgranular media detrimentally impacts mankind. In this work, we will apply novelmathematical techniques coupled with computer simulations and experiments to obtaina quantitative, predictive description of jammed materials.The outreach efforts of this project emphasize providing educational opportunities tostudents from underrepresented groups. We will organize education and recruiting tripsto predominantly female liberal arts colleges in the Northeast and historically blackschools in North Carolina, such as North Carolina Central University, and others in theSoutheast. These trips will include giving technical and popular lectures, includingdemonstrations to show that research on jammed materials is intriguing and important.During informal meetings with students we will emphasize that careers in science andtechnology are rewarding and open to those in underrepresented groups. To stimulatefurther student interest in this research, we will hold biannual 2-day lab open houses sothat promising undergraduates can be exposed to both experimental and theoreticalaspects of our research. To encourage close collaboration among researchers in thefield of jammed materials, we will organize biannual interdisciplinary workshops. Theinaugural workshop, ``Computational Homology Tools Applied to Jamming and Flow inGranular Materials'' is scheduled for the winter of 2009.