Athermal Shear-Driven Flow of Mixtures of Frictionless Rods and Disks in Two Dimensions*

We numerically simulate the athermal steady-state shearing of a mixture of frictionless circular disks and elongated spherocylinders (rods) in two dimensions, suspended in a host medium. We study behavior as the total packing fraction and the fraction of rods are varied, at slow shear strain rates. We find that the average angular velocity of the shear-driven rod rotations decreases, and the extent of the nematic ordering of the rods increases, as the fraction of the rods decreases. In the limit of a single rod in a sea of disks, the rod appears to cease rotating, except at very low packing fractions. We find that, as one shears from an initial random configuration, the system tends to form clusters of parallel contacting rods. We believe that such clusters form so as to reduce the pressure in the system, and that these clusters play an important role in the shear-driven rotation of the rods.