Proposal Numbers: 0625890 and 0625149 Principal Investigators: Losert, Wolfgang and O'Hern, Corey S. Affiliations: University of Maryland College Park and Yale University Proposal Title: Collaborative Research: Visualizing the aging process in granular matter using experiment and simulation
Intellectual merit
The goal of this project is to investigate in experiment and simulation how a jammed three dimensional system of particles slowly rearranges in response to applied forces. Aging and memory affect under what forcing a jammed arrangement of particles will start to flow, and how it will flow. An improved fundamental understanding of how jammed granular matter starts to flow may lead to advances in the processing, transport, and storage of these systems, which includes a large fraction of industrial raw materials, food, and pharmaceutical products. Specific advances may include 1) prevention of catastrophic failure of heaps of granular media even after prolonged storage, 2) optimized civil engineering procedures for the settling of soil, and 3) a better understanding of highly cohesive jammed nanoparticles for nanotechnology applications. Aging in granular matter is accompanied by notable creep or compaction large enough to cause rearrangements in the particle contact network. While microscopic models of aging due to creep and strengthening of individual particle contacts exist, these models do not account for such changes in the contact network. This project will attempt to understand how rearrangement events can lead to changes in bulk material properties and whether this can be the dominant mode in the aging process in a real material. The proposed approach is to directly image three dimensional particle rearrangements, and to compare particle motion with dynamics observed in simulation (where different aging laws can be introduced) under the same forcing. 3D arrangements will be imaged using two state-of-the-art techniques which provide information about fluid immersed and dry granular matter: laser sheet scanning of fluid immersed granular matter allows for systematic scans of large data volumes. x-ray synchrotron microtomography permits imaging of dry granular matter. A new approach from biology, fluorescence resonance energy transfer (FRET), will be used to determine key features of the contact network directly.
Broader Impact
The experimental data on 3D particle rearrangements during aging will be made available on a website for comparison to others carrying out experimental, numerical, or theoretical work on aging. Through this project new scientists will be trained to use powerful experimental techniques - confocal microscopy, x-ray tomography, and FRET and state of the art simulations. Synchrotron data taking at the European synchrotron will add to the student international experience. Demonstration materials will also be developed to highlight the complex and unexpected properties of granular flows. These demos will be used in undergraduate courses, university open houses, and public lectures. Undergraduate student involvement in the proposed research will strongly be encouraged.
