Effect of vibration on solid-to-liquid transition in small granular systems under shear

The effect of vibration on the solid-to-liquid-like transition of a dense granular assembly under planar shear is studied numerically using soft particle molecular dynamics simulations in two dimensions. We focus on small systems in a thin planar Couette cell, examining the bistable region while increasing shear, with varying amounts of vertical vibration, and determine statistics of the shear required for fluidization. In the absence of vibration, the threshold value of the shear stress depends on the preparation of the system and has a broad distribution. However, adding periodic vibration both lowers the mean fluidization threshold value of the shear stress and decreased its variability. A previous study performed similar simulations using random noise; the results from these two studies exhibit excellent agreement with proper normalization over appropriate ranges of parameters.