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Avalanche and chaotic flow in sheared granular materials

Commonly, granular materials yield or flow if sufficiently large shear stress is applied, leading to avalanche-like behavior. For experimentally sheared media, we seek to understand the relation between the macroscopic avalanche behavior and the evolution of the microscopic granular structure on one side and the flow singularities on the other side.
Commonly, granular materials yield or flow if sufficiently large shear stress is applied, leading to avalanche-like behavior. For experimentally sheared media, we seek to understand the relation between the macroscopic avalanche behavior and the evolution of the microscopic granular structure on one side and the flow singularities on the other side.
In this work, force networks and displacement fields are measured both on two and three-dimensional sheared material for both cyclically and continuously photoelastic and hydrogel sheared particles. Avalanches, their size, location and duration are extracted at the global scale from the rapid variation of the macroscopic pressure whereas at the local scale they are measured form the energy drop in each particle. From the displacement field, vorticity and curvature fields are computed along with the creation, annihilation and trajectories of the elliptical and hyperbolic points of the flow. Statistics of those differents quantities are computed and correlated to test their intrisic entanglement.

Author(s):

Jonathan Bares    
Duke University
United States

DengMing Wang    
Duke University
United States

Dong Wang    
Duke University
United States

Robert Behringer    
Duke University
United States