## Research Abstracts Online

January 2009 - March 2010

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### University of Minnesota Twin Cities

Institute of Technology

Department of Civil Engineering

St. Anthony Falls Laboratory

# PI: Kimberly M. Hill

### Discrete Element Model for Densely Flowing Granular Mixtures

The discrete element method (DEM) is the most commonly used model for dense granular flow. The DEM models granular materials by approximating interparticle forces and subsequent numerical integration. At every time step, external forces are calculated for every particle; the resultant motion is determined through numerical integration, and all particles are subsequently tracked through each computational experiment. The DEM has been shown to represent the physics of granular flow reasonably well, but it is time intensive. A constitutive model for granular flow that could predict large-scale system movements from local or global excitations would be useful for a wide range of basic and applied research questions. Unfortunately, no such model exists.

The focus of this research is to build on and improve a DEM code developed by the researchers and to develop a predictive model for granular mixtures for certain cases. In particular, the objectives are: to build a model for the dependence of the macroscopic system properties for densely flowing granular mixtures on the particle properties and "microscopicâ€ť particle motion; to develop a mechanistic model for tests of unbound materials used in roadbeds; to build a model for debris flow; and to improve the size (number of particles per experiment) and speed of the simulations. Recent work has involved computational studies in simple systems such as parallel shear cells, split bottom cells, and rotating drums to study segregation and emerging rheology in binary particulate mixtures.

### Group Members

Fan Yi, Graduate Student

Bereket Yohannes, Graduate Student