Dynamics and Rheology of Cohesive and Deformable Materials, Jamming and Flow in a Hopper

Publication Reference: 
Author Last Name: 
Robert P. Behringer
Report Type: 
Research Area: 
Wet Systems
Publication Year: 
Publication Month: 
United States

Throughout the course of this grant, we have carried out extensive experiments, and to a certain extent, theoretical studies, that pertain to the flow of grains (typically tri-disperse disks) in a quasi-2D hopper. This material was summarized extensively for the IFPRI-NSF Collaboratory, and the present report is based largely on that summary. I note that since the submission of the report for the Collaboratory, we have carried out additional studies of the velocity and density fields for our hopper flows. These studies use both particle tracking (PIV) and convolution techniques to obtain the velocity field on relatively short time scales, i.e. time scales short enough to capture detailed fluctuations. These fluctuations are of interest to the extent that they play a role in determining the overall flow properties. The two different velocimetry techniques yield data on finer and coarser spatial scales, respectively for the PIV and convolution methods. This work is nearing completion and will be part of a comprehensive manuscript that we are now preparing. Initial phases of this work were described in Jamming and Flow in 2D Hoppers, J. Tang, S. Saghdipour, and R.P. Behringer, Powders and Grains p. 515-518 (2009), ed. M. Nakagawa and S. Luding. It is also anticipated that the outcome of the IFPRI-NSF Collaboratory, which will be based, in part, on these studies will lead to an additional publication. This work has also been presented at roughly a half-dozen technical meetings (outside IFPRI). Finally, we have recently obtained a DEM code from Prof. Marcos Salazar (U of Bourgogne) which we are adapting to our hopper system. Hence, we will be able to also contribute to the modeling effort associated with the Collaboratory, and I anticipate using this code for the studies in the new IFPRI Grant.