Research – Granular materials

A primary focus of my research has been the study of dense granular materials during flow. So far, granular materials have resisted a complete theoretical description, and compared to other states of matter, such as solids and fluids, relatively little is known about them.

A key component of granular materials is their geometry: the particles form a random packing, and an individual particle is strongly geometrically constrained by its neighbors. To account for this, my group developed the spot model of granular flow, based on the concept that in order to flow, particles must move co-operatively. Our simulations were able to reproduce flowing random packings in hopper drainage at a fraction of the computational cost. Since then we have been trying to better understand the microscopic physics behind granular materials, in the hope of creating a rapid, general simulation technique.


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Simulations of the spot model

Learn about my work on creating a multiscale simulation of dense granular drainage using the spot model, summarizing our paper Dynamics of Random Packings in Granular Flow published in Physical Review E, 2006.

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Stress, strain rate, and free volume

A short article describing recent work on material properties in granular flow, with the aim of constructing a better continuum theory, or a general multiscale simulation technique.

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A coupled continuum/discrete model of granular flow

This page contains some notes of a new simulation I have been writing, containing a continuum elastoplastic model of granular flow coupled to a discrete mechanism for particle motion.

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Voronoi volumes and local density

A short article on our work using Voronoi cells as a method of very accurately calculating free volume in a granular material on a local scale.

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Granular flow in a pebble-bed reactor

A summary of our work on full-scale discrete element simulations of a pebble-bed nuclear reactor design, done in collaboration with Sandia National Laboratories, described in our paper Analysis of Granular Flow in a Pebble-Bed Nuclear Reactor, published in Physical Review E, 2006.