Analyzing The Flow of a System of Spheres Using Shape-Anisotropic Particles

We report here on a simulation conducted using LAMMPS [https://lammps.sandia.gov] of a small concentration of dimers in a gravity-driven flow of spheres. The simulation box is a quasi-2D vertical hopper with a rectangular outlet containing a 1% concentration of dimers in an equal mixture of frictional spheres of diameter ratio 1.2. Each dimer consists of two contacting spheres glued together, and all spheres undergo the same Hertzian contact interactions. We track the positions, velocities and orientations of the dimers relative to the flowing spheres and find that while the flow is collisional, the dimers do not reorient significantly except near the walls and near the outlet, where the fluctuations in the sphere velocities are higher. However, as outlet size changes, the region with the largest reorientation per dimer moves from near the edges for large openings, to near the center for small openings, thus appearing to track where velocity fluctuations are large.