Self-diffusion of spherocylindrical particles flowing under non-uniform shear rate.

Abstract

This work is devoted to study numerically the self-diffusion of spherocylindrical particles flowing down an inclined plane, using the discrete element method (DEM). This system is challenging due to particles being non-spherical and because they are subjected to a non-uniform shear rate. We performed simulations for several aspect ratios and inclination angles, tracking individual particle trajectories. Using the simulation data, we computed the diffusion coefficients <i>D</i>, and a coarse-graining methodology allowed accessing the shear rate spatial profiles <i></i>(<i>z</i>). This data enabled us to identify the spatial regions where the diffusivity strongly correlates with the local shear rate. Introducing an effective particle size <i>d</i>_⊥, we proposed a well-rationalized scaling law between <i>D</i> and <i></i>. Our findings also identified specific locations where the diffusivity does not correlate with the shear rate. This observation corresponds to zones where <i></i> has non-linear spatial variation, and the velocity probability density distributions exhibit asymmetric shapes.