Dynamics of an intruder moving through a confined granular medium: Rescaled packing fraction yields data collapse for different intruder and system sizes.
ORAL
Abstract
We consider an intruder dragged by a spring though a layer of bidisperse disks constrained in a fixed volume Couette cell in both discrete element simulations and experiments. The spring is loaded slowly, leading to stick-slip dynamics of the intruder. As the intruder advances, the medium develops large density heterogeneities, with a region in front of the intruder more densely packed and a region behind the intruder depleted of particles. We explore a range of annulus widths W, intruder sizes D, and global packing fractions Φ and measure the fluctuating force on the intruder. We find that an effective packing fraction, defined as Φeff = Φ W / (W - D), can account for the combined effect of the three variables, collapsing the data to a single curve. When Φeff is equal to the steady-state packing fraction of quasi-statically sheared packings under fixed confining pressure, the disks pack after some time into annular regions outside the intruder's path, leaving a channel that allows for unimpeded motion of the intruder. Increasing values of Φeff lead to increasing average forces and longer sticking periods as the intruder finds difficult to clear an open channel through which to move.
*ARO Grant No. W911NF1810184.
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Presenters
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Luis A. Pugnaloni
- Departamento de Física, Facultad Ciencias Exactas y Naturales, Universidad Nacional de La Pampa, CONICET, Santa Rosa (La Pampa), Argentina
- Departamento de Física, Universidad Nacional de La Pampa, CONICET, Argentina