(756a) Flow Simulations of Size Disperse Granular Particles with Realistic Contact Models

Accurate and general constitutive models of granular material flow would aid experimental flow characterization measurements, but yet remain elusive. Flow field, size and shape dispersity, roughness and contact mechanics change the behavior of flowing granular material and challenge existing constitutive models. Particularly, granular materials in nature and industry are rarely monodisperse and often exhibit complex distribution in particle sizes. To support the development of transferable constitutive models, we perform particle-based stress-controlled discrete element modeling simulations of particles with varying degrees of size bidispersity. Simultaneously, we also extend the simple, yet widely-used, spring-dashpot contact mechanics model by including constraints on other modes of motion. The shear stress-to-pressure ratio , density and coordination number are measured. It has been previously shown that, with slight modifications, the constitutive rheological model for monodisperse particles is applicable to granular flows with moderately polydisperse particles. Here we assess the validity of the model for extreme size bidispersity — up to 40:1 size ratio. Using our stress-controlled simulation method, we also examine flow anisotropy in such large size disperse granular flows, which is assumed to be isotropic in the standard model. Lastly, we find that the critical shear stress and flow anisotropy qualitatively changes with increasing strain rate and friction.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology &Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2021-3774 C