Flow and rheology of frictional elongated grains

Abstract

The rheology of a 3-dimensional granular system consisting of frictional elongated particles was investigated by means of discrete element model (DEM) calculations. A homogenous shear flow of frictional spherocyliders was simulated, and a number of rheological quantities were calculated. In the framework of the µ(I) rheology, the effective friction was found to be a non-monotonic function of the aspect ratio for interparticle friction coefficient µp 0.4, while it was an increasing function for larger µp. We reveal the microscopic origin of this peculiar non-monotonic behavior. We show the non-trivial dependence of the velocity fluctuations on the dissipation regime, and trace back the behavior of the normal stress differences to particle-level quantities.

Kinematics and shear-induced alignment in confined granular flows of elongated particles

“…Overall, we note a systematic increase of S with the aspect ratio of the particles. This tendency of reaching a higher orientational order in systems composed by more elongated particles is consistent with numerical results obtained in sheared granular systems composed of 2D dumbbells [21], elongated rods [18,44], long clumps of overlapping spheres [23,24], ellipses [26], ellipsoids [45] and spherocylinders [19,43,45], as well as with experimental results obtained with rice grains and rod like particles [23,24].…”

Lees-Edwards boundary conditions for the multi-sphere discrete element method

“…The third shape considered here is a simple dimer or dumbbell particle, formed by fixing two identical spheres together with no overlap, see Figure 3c. This elongated particle shape was chosen so that qualitative comparisons can be made to data provided in the available literature Nath and Heussinger [14], Nagy et al [15], Salerno et al [16], Nagy et al [18].…”

“…Recent literature indicates that constitutive models developed for spherical particles [11][12][13], appear amenable for extension to aspherical particles [14][15][16][17][18]. Moreover, it is now well established that particle morphology causes complex microstructural behaviour [19][20][21][22][23] and significantly influences the properties [24][25][26][27][28] of granular materials.…”

A generalized model for dense axisymmetric grains flow with orientational diffusion

“…(2017) and Nagy et al. (2020) using DEM, where it was shown that the rheological response has a strong dependency on the microstructure contacts and collisions which are primarily a function of the grains’ orientation, alignment and shape. Based on these observations, an anisotropic rheology model (Nadler 2021) was proposed that accounts for the microstructure orientation.…”

“…To mathematically model the tendency of axisymmetric grains to align, a kinematic continuum model that captures the evolution of grains orientation subjected to homogenous flow was introduced in Nadler, Guillard & Einav (2018). In addition, the rheology of axisymmetric grains was investigated in Berzi et al (2016Berzi et al ( , 2017, Trulsson (2018), Nath & Heussinger (2019), Nagy et al (2017) and Nagy et al (2020) using DEM, where it was shown that the rheological response has a strong dependency on the microstructure contacts and collisions which are primarily a function of the grains' orientation, alignment and shape. Based on these observations, an anisotropic rheology model (Nadler 2021) was proposed that accounts for the microstructure orientation.…”