Forces and flow induced by a moving intruder in a granular packing: coarse-graining and DEM simulations versus experiments

Abstract

The study of stress transmission and particles' mobility in powder beds constitutes a challenging issue to improve processes such as milling, agglomeration and kneading. In this paper the ability to promote particle mobilities by means of an intruder is investigated. An experimental setup was developed to characterize the particles' mobility at the voxel scale. A Particle Image Velocimetry (PIV) algorithm was employed to determine the velocity fields in the vicinity of an intruder in ascendant vertical motion. A Discrete Element Method (DEM) model was developed to simulate the same system at the particle scale. Velocity maps were determined relying on a coarse-graining procedure and compared to PIV results. During the rise of the intruder the experimental and simulated drag forces are in good agreement. Spatiotemporal correlation between the granular mobility and the state of the force network are analyzed as a function of the height of the intruder. The drag force profile exhibits a relaxation trend, noised by fluctuations whose origin are in successive loading/rupture events. An interpretation of these fluctuations is proposed with regard to the development of preferential paths in the normal force network, and to the localization of sliding at the contacts scale. Finally, we show that global strains are a consequence of the ejection of particles directly in contact with the ends of the intruder.

Anisotropic frictional model for an object sliding in a granular media

“…where the ratio A c /A m ≈ 5% for our cylinder and ϵ = 3 is a constant parameter that has been determined to best fit our measurements. The fact that the parameter ϵ is greater than one can be associated with the fact that the movement of the tip of the cylinder displaced a larger volume of grains relatively to a surface along the cylinder, in agreements with the results of DEM simulations 43 . Then, the perpendicular friction coefficient is deduced deriving Eq.…”

Linking dynamics between anchors and granular materials

“…Over the last decade, a significant number of numerical work has been performed to investigate the failure mechanism of the anchor and the linking properties between the anchor and the granular materials [5,6]. In which, the drag force is known as a principal investigator, acting on the anchor during its pullout process has been extensively studied [7,8]. Basically, this drag force increases with increasing the size and the embedment depth of the anchor in both quasi-static regime and dynamic regime [9].…”