Nathalie Fraysse

Numerical simulations of the maximum angle of stability of bi-disperse cohesive granulates

We performed molecular dynamics simulations of the maximum angle of stability of a bi-disperse granulate with cohesion (either springs or constant inter-particular forces) in a rotating drum. Segregation has been avoided by computing only the first angle of maximum stability after the rotating drum started its rotation. The results show that larger cohesive forces have to be applied in order to recover the same avalanche angle as for a mono-disperse granulate.

Melde’s Experiment on a Vibrating Liquid Foam Microchannel

We subject a single Plateau border channel to a transverse harmonic excitation, in an experiment reminiscent of the historical one by Melde on vibrating strings, to study foam stability and wave properties. At low driving amplitudes, the liquid string exhibits regular oscillations. At large ones, a nonlinear regime appears and the acoustic radiation splits the channel into two zones of different cross section area, vibration amplitude, and phase difference with the neighboring soap films. The channel experiences an inertial dilatancy that is accounted for by a new Bernoulli-like relation.

Response of a cohesionless packing to a point load

In order to study the mechanical behaviour of grain piles, we investigate the response of a non‐cohesive two‐dimensional packing of cylinders submitted to a localized force, that in the reversible regime of deformation. By means of image processing, we obtain an accurate measurements of the individual grain displacements. The measured displacement field deviates unambiguously from the predictions of linear continuum elasticity. Instead, the data reveal a localization process, as well as a partial agreement with the diffusive models of Harr (1966) or of Coppersmith et al. (1996).

Mechanichal Behavior of a Noncohesive Packing at Small Deformations: Deviation From Continuum Elasticity

In order to specify the mechanical behavior of grain piles, we investigate the response of a non‐cohesive bidimensional packing of cylinders submitted to a point load. By means of image processing, we have an accurate access to the individual grain displacements in the reversible regime. The measured displacement field deviates unambiguously from the predictions of Continuum Elasticity. The data reveal a partial agreement with the diffusive models of Harr (1966) or of Coppersmith et al. (1996).