We conduct molecular dynamics simulations of athermal systems undergoing boundary-driven planar shear flow in two and three spatial dimensions. We find that these systems possess nonlinear mean velocity profiles when the velocity u of the shearing wall exceeds a critical value uc. Above u c, we also show that the packing fraction and mean-square velocity profiles become spatially dependent with dilation and enhanced velocity fluctuations near the moving boundary. In systems with overdamped dynamics, uc is only weakly dependent on packing fraction φ. However, in systems with underdamped dynamics, uc is set by the speed of shear waves in the material and tends to zero as φ approaches φc, which is near random close packing at small damping. For underdamped systems with φ < φc, uc is zero; thus they possess nonlinear velocity profiles at any nonzero u.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)