Collaborative Research: Drag Rules for Quasi-Static Granlar Media - Experimental and Numerical Studies

Emory University, Atlanta GA

Investigators

Abstract

ABSTRACT Proposal Numbers: 0626191 and 0625139 Principal Investigators: Koehler, Stephan and Santamaria, J. Carlos Affiliations: Emory University and Georgia Tech Research Corporation Proposal Title: Collaborative Research: Drag Rules for Quasi-Static Granular Media Experimental and Numerical Studies Intellectual Merit: The flow of dense granular matter is technologically important, but poorly understood. Competing models of dense granular matter are based upon different physical assumptions, that have enough free parameters to allow for general agreement with experimental observations. The number of experimental model systems is relatively small, and they are typically characterized by a high degree of symmetry involving simple flows, such as plane shear or Couette flow. In order to advance understanding of dense granular flow, a larger and richer variety of model systems needs to be considered. Two research teams, one from the Emory physics department and another from the Georgia Tech civil engineering department will collaboratively investigate the dynamics of intruders in dense granular media. Four inter-related projects are proposed: 1) Force and flowfield measurements of intruders moving vertically through static granular media, 2) Dependence of drag forces on the intruder's orientation, 3) Variations of intruder drag forces due to shearing of granular matter, and 4) Interactions between two intruders mediated through the granular medium. The Emory team will perform the physical experiments; the Georgia Tech team will simulate these four systems using a commercially available discrete element code and the equivalent frictional continuum Cam Clay model. The experimental results will verify that the code is accurate, and the numerical simulations will provide insight into experimentally inaccessible quantities, such as the flow fields and fabric. The proposed studies will provide phenomenological rules for the resistive forces on intruders, and the results will enable theorists to determine the validity of physical assumptions upon which their models are based. These rules will be of practical use for developing new methods of handling granular matter and for understanding how certain desert animals swim through sandy environments. Broader Impact: Procedures will be developed for determining the in situ, local rheology within granular beds based upon intruder drag. These procedures will enhance processing of granular matter in many different settings, varying from conveyer belts to mixing of pharmaceutical powders. This program will build an exciting, synergistic and interdisciplinary environment, by combining teams from two different universities and disciplines, with each team studying the same systems but using different approaches. These interactions will also prompt inter-disciplinary teaching of a soft condensed matter physics course and a fundamentals of granular matter course. Additional activities include undergraduate and graduate research participation, creation of web-based teaching modules, and interactions with desert biologists.