Quasiperiodic compaction events in a two-dimensional frictional model.

Area of Science:

• Physics of granular materials
• Complex systems dynamics
• Computational physics

Background:

• Avalanche precursors, characterized by quasiperiodic surface displacements, are observed during the slow inclination of granular beds.
• Despite experimental study since the mid-2000s, these precursors have been challenging to model numerically.
• Previous attempts include simplified one-dimensional models, which do not fully capture the complexity of experimental setups.

Purpose of the Study:

• To develop a more realistic two-dimensional numerical model for simulating avalanche precursors.
• To investigate the underlying mechanisms and quantitative relationships governing precursor events in granular systems.
• To bridge the gap between simplified 1D models and complex 3D experimental observations.

Main Methods:

• A two-dimensional discrete element model was created, simulating disks on a frictional plane with granular molecular dynamics interactions.
• The model incorporates interactions between neighboring disks and boundaries.
• Simulations were conducted under slow inclination of the granular bed to observe precursor events.

Main Results:

• The model robustly reproduces quasiperiodic compaction events, identified as avalanche precursors.
• The angular period between events is directly proportional to the difference between static and dynamic friction coefficients.
• System size influences precursor behavior, with larger systems exhibiting decreased inclination at the initial event and reduced angular periods.

Conclusions:

• The developed 2D model provides a valuable tool for understanding avalanche precursor phenomena.
• Key parameters like friction coefficients and system size significantly impact the characteristics of precursor events.
• The model's ability to reproduce experimental observations, including cyclic inclination effects, validates its approach.