The angle of repose of spherical grains in granular Hele–Shaw cells: a molecular dynamics study

Abstract

Abstract. We report the results of three dimensional molecular dynamic simulations on the angle of repose of a sandpile formed by pouring mono-sized cohesionless spherical grains into a granular Hele-Shaw cell. In particular, we are interested to investigate the effects of those variables which may impact significantly on pattern formation of granular mixtures in Hele-Shaw cells. The results indicate that the frictional forces influence remarkably the formation of pile on the grain level. Furthermore, We see that increasing grain insertion rate decreases slightly the angle of repose. We also find that in accordance with experimental results, the cell thickness is another significant factor and the angle of repose decays exponentially by increasing the cell thickness. It is shown that this effect can be interpreted as a cross-over from two to three dimensions. In fact, using grains with different sizes shows that the behavior of the angle of repose when both size and cell thickness are varied is controlled by a scaled function of the ratio of these two variables. † corresponding author

Nonuniformities in the Angle of Repose and Packing Fraction of Large Heaps of Particles

“…As summarized in Fig. 1(b), we find such heaps to be characterized by several new geometrical features: (i) two external angles of repose and , (ii) an internal angle of repose , and (iii) four distinct density (packing fraction) regions, A, B, C, D. This means that instead of just the familiar single angle of repose [28], heaps may in fact display two distinct angles of repose, a fact implying the existence of four characteristic density zones in the heap. As for the external and internal angles of repose, and , we showed them to be interrelated according to Eq.…”

Janssen effect and the stability of quasi-two-dimensional sandpiles

“…The angle of repose start from zero and reaches very soon a stable value. Previous studies have demonstrated that the angle remains constant with further insertion of grains 14 . The growth of the height of the pile H and length L (measured from the pile profile) with grain number N in a typical cell with size w = 6 is shown in fig.3.…”

“…The effect of the cell thickness w on the stability of a confined sandpile has been the subject of both experimental and numerical studies [9][10][11][12][13][14] . Careful experiments and measurements reveal that the presence of front and rear walls increases greatly the angle of repose θ as well as the maximal angle of movement θ m (the maximal angle that a granular medium can reach when carefully tilted).…”

“…On the other hand, inserting grains into a cell with at least one open boundary, generates a stable heap with finite slope. This non-zero angle to the horizontal, the angle of repose θ, is one of the most important characteristic of the granular material at macroscopic scales [8][9][10][11][12][13][14][15][16] .…”

Characteristics of large three-dimensional heaps of particles produced by ballistic deposition from extended sources

“…As summarized in Figure 2(f), the novel geometrical properties Downloaded by [University of Miami] at 09: 21 27 December 2014 are as follows: (i) two external angles of repose α and β, (ii) an internal angle of repose γ , and (iii) four distinct density (packing fraction) regions, A, B, C, D. In other words, instead of just the familiar single angle of repose [42], heaps may in fact show two distinct angles, a fact that implies the existence of four distinct density zones in the heap. Such properties can be recognized both in the density distribution and in the distribution of the number of contacts.…”