Velocity and Shear Stress Profiles of a Sheared Athermal System with Pins

We use molecular dynamics simulations to study a two-dimensional athermal, bidisperse system of particles with purely repulsive harmonic interactions. Via the motion of rough top and bottom walls composed of frozen particles, we shear the system at a constant rate. Energy is dissipated via a damping force

F^D= -b (r_ij/r_ij .v_ij) r_ij/r_ij

The system furthermore has fixed degrees of freedom in the form of ‘pins.’ The size ratio of pins : small particle : large particle is 0.004:1:1.4. Pins are located on a square lattice. We study the microscopic and macroscopic properties of our system with and without pins in response to shearing. We show preliminary results for pressure and shear stress as function of shear rate and packing fraction. We show velocity and local shear stress profiles. Microscopically, we find that pins impede the propagation of velocity and shear stress far from the walls.Furthermore we study the time evolution of D²_min and its relation to the contact number.