In-depth influence of the top surface fabrication of a bead packing.

Packings of beads confined in slowly tilted containers with a top free surface are commonly used in laboratory experiments to model natural grain avalanches and better understand and predict critical events from optical measurements of the surface activity. To that aim, after reproducible packing preparations, the present paper focuses on the effects of the surface fabrication, which can be scraped or soft leveled, on both the avalanche stability angle and the dynamic of precursory events for glass beads of 2-mm diameter. A depth effect of a scraping operation is highlighted by considering different packing heights and inclination speeds.

Particle impact on a cohesive granular media.

We investigate numerically the impact process of a particle of diameter d and velocity V_{i} onto a cohesive granular packing made of similar particles via two-dimensional discrete element method simulations. The cohesion is ensured by liquid bridges between neighboring particles and described by short range attraction force based on capillary modeling. The outcome of the impact is analyzed through the production of ejected particles from the packing, referred to as the splash process.

Dynamic behavior of humid granular avalanches: Optical measurements to characterize the precursor activity.

Laboratory study of slope stability of granular media remains a challenge for modeling, understanding, and predicting natural hazards, such as avalanches and landslides, precursory signs of which are controlled by numerous physical parameters. The present work focuses on the impact of the humidity, in the range of 40-90%, on the stability of monodisperse dense packings of spherical beads. The beads are in a transparent box that is slowly and continuously tilted and allows simultaneous top and lateral optical measurements of global displacements of grains at the surface, defined as precursors.

Grain-scale modeling and splash parametrization for aeolian sand transport.

The collision of a spherical grain with a granular bed is commonly parametrized by the splash function, which provides the velocity of the rebounding grain and the velocity distribution and number of ejected grains. Starting from elementary geometric considerations and physical principles, like momentum conservation and energy dissipation in inelastic pair collisions, we derive a rebound parametrization for the collision of a spherical grain with a granular bed. Combined with a recently proposed energy-splitting model [Ho et al.

Segregation in a model system for tapped wet disks in two dimensions.

The problem of segregation of mixtures in a column of wet disks subjected to tapping is studied through a simple model that simulates, through a pseudo-dynamics algorithm, the formation of the packing and the successive tapping of it. The particles consist in a binary mixture of disks with two different sizes and the capillary forces are simulated stochastically by a sticking probability between the particles. We have recently shown that arch formation is one of the chief mechanisms determining size segregation in a non-convecting ensemble of dry disks (R.