Upslope migration of snow avalanches in a warming climate.

Snow is highly sensitive to atmospheric warming. However, because of the lack of sufficiently long snow avalanche time series and statistical techniques capable of accounting for the numerous biases inherent to sparse and incomplete avalanche records, the evolution of process activity in a warming climate remains little known. Filling this gap requires innovative approaches that put avalanche activity into a long-term context.

Microscopic Origin of Nonlocal Rheology in Dense Granular Materials.

We study the microscopic origin of nonlocality in dense granular media. Discrete element simulations reveal that macroscopic shear results from a balance between microscopic elementary rearrangements occurring in opposite directions. The effective macroscopic fluidity of the material is controlled by these velocity fluctuations, which are responsible for nonlocal effects in quasistatic regions.

Mean force and fluctuations on a wall immersed in a sheared granular flow.

In a sheared and confined granular flow, the mean force and the force fluctuations on a rigid wall are studied by means of numerical simulations based on the discrete element method. An original periodic immersed-wall system is designed to investigate a wide range of confinement pressure and shearing velocity imposed at the top of the flow, considering different obstacle heights. The mean pressure on the wall relative to the confinement pressure is found to be a monotonic function of the boundary macroscopic inertial number which encapsulates the confinement pressure, the shearing velocity, and the thickness of the sheared layer above the wall.

Force fluctuations on a wall in interaction with a granular lid-driven cavity flow.

The force fluctuations experienced by a boundary wall subjected to a lid-driven cavity flow are investigated by means of numerical simulations based on the discrete-element method. The time-averaged dynamics inside the cavity volume and the resulting steady force on the wall are governed by the boundary macroscopic inertial number, the latter being derived from the shearing velocity and the confinement pressure imposed at the top. The force fluctuations are quantified through measuring both the autocorrelation of force time series and the distributions of grain-wall forces, at distinct spatial scales from particle scale to wall scale.

[Consideration of the shape of the teeth in facial hyperdivergency].

Introduction: The study examines how the shape of the teeth is taken into account in the context of facial hyperdivergency. One aim was to check out the widely-held belief that the hyperdivergent patient has long teeth.

Discussion: Our study found no link between the shape of the teeth and facial hyperdivergency, thus confirming the results in the literature.

Quasistatic to inertial transition in granular materials and the role of fluctuations.

On the basis of discrete element numerical simulations of a Couette cell, we revisit the rheology of granular materials in the quasistatic and inertial regimes, and discuss the origin of the transition between these two regimes. We show that quasistatic zones are the seat of a creep process whose rate is directly related to the existence and magnitude of velocity fluctuations. The mechanical behavior in the quasistatic regime is characterized by a three-variable constitutive law relating the friction coefficient (normalized stress), the inertial number (normalized shear rate), and the normalized velocity fluctuations.

Time-varying force from dense granular avalanches on a wall.

We studied avalanches of cohesionless granular materials down a rough inclined plane and overflowing a wall normal to the incoming flow and to the bottom. This paper focuses on the transient time-varying mean force exerted by the granular stream on the obstacle at various slope inclinations. A nearly triangular dead zone is formed upstream of the obstacle.