X-Ray Tomography and MRI Studies of Three-Dimensional Granular Materials: The Roles of Particle Geometry and Interactions

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AbstractCTS-0090490H. Jaeger, University of ChicagoIt is proposed to operate jointly two diagnostic techniques to elucidate the property distribution of three-dimensional time-resolved granular flows. These are Magnetic Resonance Imaging (for velocity) and x-ray tomography (for particle density, position and orientation). So far, the MRI system available to the PI has yielded velocity fields with 100-micron resolution (i.e. 1/10-grain diameter). On that basis, it is possible to reconstruct mass flow rates. However, a full account (including particle spin, etc.) requires the synergistic use of X-ray tomography, which is also available to the PI from the new Advanced Photon Source at the DOE Argonne Laboratory (550-nm resolution). Special attention will be focussed on particle shape, contact interaction, ultrasmall ("nano") particle dynamics, and system evolution with time.The outcome of this research should provide some understanding of the settling process, and of the role of volume exclusion in reaching a final non-equilibrium distribution ("jamming"). The contribution of shape anisotropy and of cluster formation to this less-than-optimum package of particles, will be tested against the proposed accurate experiments and the recently available theories. Emphasis will be brought on three-dimensional geometry, oscillatory shear, particle interaction and mixtures (e.g. rod/spheres), ultrafine powders.