Biomedical subjects
Publications and source records attributed to Jean Rajchenbach.
The standard hydrodynamic description does not apply to the rapid flow regime of inelastic grains in the dense limit. Emphasizing the role of inelastic loss and collapse, we propose a new approach relying on a nonlocal dissipation scheme. Our model succeeds in accounting qualitatively and quantitatively for the linear profile of velocity found in experiments on dense gravity-driven flows.
We present a new theoretical approach aimed to describe the dynamical properties of avalanches. Starting from simple microscopic considerations, we propose an analytical derivation accounting for the avalanche growth as a function of time. The solution resembles very closely recent experimental observations. We show in particular that the two observed regimes of growth proceed from a singularity in the rear front velocity as a function of the slope.
We study the nucleation and the growth of avalanches in a model experimental system consisting of a bidimensional packing of noncohesive grains positioned in a rotating drum. We show that the avalanche mass increases linearly in time, and that the growth rate is governed by the velocities of the two up and down fronts. The upper front is shown to propagate upwards with a velocity which is equal to the averaged velocity of the flowing grains, whereas the velocity of the downslope propagating front is approximately equal to twice the avalanche velocity. We describe simple mechanisms which quantitatively account for the observed dynamical properties.