Fig. 2.

(A) Schematic of the soft-particle contact model used in the discrete-element calculations. Contact between each particle is characterized by normal and tangential springs and dashpots along with friction acting in the tangential direction. (B) Sketch indicating the surface of the transparent Perspex box that is tracked via high-speed photography. (C) High-speed photography measurements and corresponding predictions of the average magnitude $〈\left|v\right|〉$ of the velocities of balls over 30 cycles on the $z-x$ plane located at the $y=0$ surface of the box. These velocities are averaged over 30 cycles after steady-state crystallization has been attained for vibration at an amplitude $ɑ=2 \text{mm}$ and two frequencies ƒ = 20 Hz and 90 Hz. The predictions and measurements are restricted to the height of the original stationary assembly for 90 Hz. (D) Predictions of the effective strain rate ${\dot{\epsilon }}_e$ within the 3D granular assembly. The predictions are shown on the on the $z-x$ plane located at $y=L/2=6\mathrm{c}\mathrm{m}$ for vibration with an amplitude $ɑ=2 \text{mm}$ at ƒ = 20 Hz and 90 Hz. The temporal evolution of the strain rate is shown by plotting the spatial distributions of ${\dot{\epsilon }}_e$ averaged over five cycles at selected stages prior to the assembly attaining steady-state crystallization. Alongside, we also show the discrete particle structure with the particles colored to indicate the crystal structure they are deemed to lie within.