Model of the saltation transport by Discrete Element Method coupled with wind interaction

Institut de Physique de Rennes, UMR UR1-CNRS 6251, Université de Rennes1, 263, Avenue du Général Leclerc, Campus de Beaulieu,CS 74205, 35042 Rennes Cedex, France

^* e-mail: luc.oger@univ-rennes1.fr
^** e-mail: alexandre.valance@univ-rennes1.fr

Published online: 30 June 2017

Abstract

We study the Aeolian saltation transport problem by analysing the collision of incident energetic beads with granular packing. We investigate the collision process for the case where the incident bead and those from the packing have identical mechanical properties. We analyse the features of the consecutive collision process. We used a molecular dynamics method known as DEM (soft Discrete Element Method) with 20000 particles (2D). The grains were displayed randomly in a box (250X60). A few incident disks are launched with a constant velocity and angle with high random position to initiate the flow. A wind velocity profile is applied on the flowing zone of the saltation. The velocity profile is obtained by the calculi of the counter-flow due to the local packing fraction induced by the granular flow. We analyse the evolution of the upper surface of the disk packing. In the beginning, the saltation process can be seen as the classical “splash function” in which one bead hits a fully static dense packing. Then, the quasi-fluidized upper layer of the packing creates a completely different behaviour of the “animated splash function”. The dilation of the upper surface due to the previous collisions is responsible for a need of less input energy for launching new ejected disks. This phenomenon permits to maintain a constant granular flow with a “small” wind velocity on the surface of the disk bed.