CEE Graduate Seminar Series Guest Speaker: David Henann, Brown University

Wednesday, October 25, 2017
12:00 pm to 1:00 pm
Floor/Room #: 
1st Floor - 116

cee-vrbannerDATE:   Wednesday, October 4, 2017

TIME:    12:00 – 1:00pm

ROOM:   KH-116

Topic:  A continuum model for steady flows of dense granular materials



David Henann

Brown University






Dense, dry granular flows display many manifestations of grain-size dependence in which cooperative effects at the microscopic grain-level

have an observable impact on the macroscopic flow phenomenology. In one class of phenomenology, the characteristic length-scales

associated with dense granular flow velocity fields in a wide variety of geometries are strongly dependent on the grain-size. In a second class

of phenomenology, dense granular materials display size-dependence of the flow threshold. For example, flows of thin layers of grains down

an inclined surface exhibit a size effect whereby thinner layers require more tilt to flow. Neither of these classes of behaviors may be captured

by local, scale-independent constitutive theories, and hence, the formulation of a predictive model for dense granular flow has proven to be

particularly difficult. In this talk, we present a continuum-level constitutive model for steady flow - called the nonlocal granular fluidity model –

aimed at filling this need. The key ingredient of the model is a grain-size-dependent, nonlocal contribution, in which flow at a point is affected

by both the local stress as well as the flow in neighboring material. We then demonstrate that the model quantitatively captures the size-

dependence of both steady flow fields and the flow threshold - i.e., the conditions under which steady flow is possible - by comparing model

predictions to measurements from experiments and discrete element method calculations. Throughout, we emphasize the geometric

generality of the model by considering flows in a wide variety of configurations, including annular shear flow, planar shear flow with gravity,

vertical chute flow, inclined plane flow, heap flow, and all variations of annular split-bottom flow.



 David L. Henann is the James R. Rice Assistant Professor of Engineering 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. His research interests are in the

area of theoretical and computational solid mechanics, focusing on the modeling of amorphous materials, such as metallic glasses, granular

materials, and polymeric elastomers, and addressing issues of size-effects and multi-physics coupling. Henann is the recipient of an NSF

CAREER Award and the 2016 Pi Tau Sigma Gold Medal from the American Society of Mechanical Engineers (ASME). He was honored for

his teaching by the students of Brown University Tau Beta Pi with the 2016 School of Engineering Dedicated Faculty Award.

Cindy Bergeron
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