arXiv subjects

Michele Larcher

Publications and source records attributed to Michele Larcher.

3 recordsLinked to original sources

arXiv2026

Complex segregation patterns in confined nonuniform granular shearing flows

When polydisperse granular systems are sheared, the transverse dynamics is characterized by the interplay of size segregation and diffusion. Segregation in nonuniform and confined shearing flows is studied using annular shear cell experiments complemented with discrete numerical simulations of bidisperse, inelastic, and frictional spheres under gravity. We explored the role of shear localization, granular temperature, boundaries, and mixture properties in the evolution of the segregation rate and the maximum degree of segregation achieved by a bidisperse granular system in the steady state. A faster segregation process and a more developed degree of segregation is observed for bidisperse mixtures with a larger size ratio and a higher proportion of large particles. Normally, in the presence of gravity, size segregation induces large particles to rise and small particles to sink. However, two additional complex segregation patterns were found: inverse segregation and horizontal segregation. The first might be related to the kinematics of the flow, while the second is a geometrical effect. This additional segregation mechanism, in addition to diffusion fluxes and high confining pressure, hampers complete segregation in the steady state, where some degree of mixing always persists.

cond-mat.other↗

arXiv2022

Self-diffusion in inhomogeneous granular shearing flows

In this letter, we discuss how flow inhomogeneity affects the self-diffusion behavior in granular flows. Whereas self-diffusion scalings have been well characterized in the past for homogeneous shearing, the effect of shear localization and nonlocality of the flow has not been studied. We therefore present measurements of self-diffusion coefficients in discrete numerical simulations of steady, inhomogeneous, and collisional shearing flows of nearly identical, frictional, and inelastic spheres. We focus on a wide range of dense solid volume fractions, that correspond to geophysical and industrial shearing flows that are dominated by collisional interactions. We compare the measured values first, with a scaling based on shear rate and, then, on a scaling based on the granular temperature. We find that the latter does much better than the former in collapsing the data. The results lay the foundations of diffusion models for inhomogeneous shearing flows, which should be useful in treating problems of mixing and segregation.

cond-mat.soft↗

arXiv2021

Self-Diffusion Scalings in Dense Granular Flows

We report on measurements of self-diffusion coefficients in discrete numerical simulations of steady, homogeneous, collisional shearing flows of nearly identical, frictional, inelastic spheres. We focus on a range of relatively high solid volume fractions that are important in those terrestrial gravitational shearing flows that are dominated by collisional interactions. Diffusion over this range of solid fraction has not been well characterized in previous studies. We first compare the measured values with an empirical scaling based on shear rate previously proposed in the literature, and highlight the presence of anisotropy and the solid fraction dependence. We then compare the numerical measurements with those predicted by the kinetic theory for shearing flows of inelastic spheres and offer an explanation for why the measured and predicted values differ.

cond-mat.soft↗