Granular systems that consist of particles of disparate size segregate based on size during flow, resulting in complex, coupled segregation and flow fields. The ability to predict how granular mixtures segregate is important in the design of industrial processes and the understanding of geophysical phenomena. At the continuum level, the two primary drivers of size-segregation are pressure gradients and strain-rate gradients. In this talk, we discuss the formulation of a continuum model for the dynamics of segregation in bidisperse, dense granular flows that accounts for both driving mechanisms. Selected data from discrete-element method (DEM) simulations of dense, bidisperse granular flows are used to inform continuum constitutive equations for the relative flux of large and small particles. When combined with the nonlocal granular fluidity (NGF) model (a nonlocal rheological model for dense granular flow), the coupled model is capable of quantitatively predicting segregation and flow fields over a variety of flow geometries, including flow down a long vertical chute, flow down a rough, inclined surface, and annular shear flow.

 

David L. Henann is the James R. Rice Associate Professor of Solid Mechanics at Brown University. He received his B.S. in Mechanical Engineering from Binghamton University in 2006, followed by his S.M. and Ph.D. in Mechanical Engineering from MIT in 2008 and 2011, respectively. After postdoctoral appointments at MIT and Harvard, he joined the faculty at Brown University in the fall of 2013. Henann is the recipient of an NSF CAREER Award, the 2016 Pi Tau Sigma Gold Medal from the American Society of Mechanical Engineers (ASME), and the 2020 Eshelby Mechanics Award for Young Faculty.

 

 

Henann’s research focuses on the formulation of new continuum-level constitutive theories for describing material behavior and the application of models to engineering problems through numerical simulation. Specific problems of interest include (1) constitutive models for flow and size-segregation in dense granular materials, (2) constitutive modeling of porous elastomers, and (3) modeling of inertial microcavitation in soft materials.