Friction Based Segregation Of 2D Granular Assembly
- PDF / 445,033 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 104 Downloads / 213 Views
***painter(phy.duke.edu;
ABSTRACT We present theoretical, computational (molecular dynamics), and experimental results describing the dynamical properties of a set of monodisperse, spherical particles confined to a two dimensional surface. An interaction model, which includes the interaction between the particles via collisions as well as the interaction with the substrate, shows that the properties of this granular system are influenced significantly by the latter. In particular, we analyze in detail the effects of slipping and rolling friction, which are usually overlooked. Theoretically, we explore the possibility of formulating a continuum, hydrodynamic-like theory applicable to this system. Further, we apply our model to the particular problem of a system of two kinds of particles with different frictional properties. Our experiments have found that friction-based segregation of particles moving on a horizontally shaken substrate can be achieved. Computational results give further insight into this novel segregation mechanism and confirm that careful and realistic modeling is needed in order to understand this effect. INTRODUCTION Much of the recent work in exploring the dynamics of the granular materials has been concentrated on vertically vibrated granular systems. Many interesting effects, such as segregation by size, pattern formation, convection, to name just a few, have been observed. Although there have been some studies [1], much less is known about the corresponding dynamics of granular materials subjected to horizontal vibrations. In our previous work [2], we looked into the dynamics of a horizontally shaken 3D granular system. Here, we concentrate on the seemingly simple system of a single layer of particles on a 2D inclined surface which is being vibrated in horizontal direction. In recent experimental work [31, where the system was energized by an oscillating side-wall, clustering of the particles has been observed. In our experiments, we subject the whole system to horizontal shaking. Furthermore, the particle assembly consists of two kinds of (spherical) particles. Half of the spheres are highly smooth, while the remainder are identical to the first half, except that their surface is roughened by chemical etching, giving them a higher coefficient of rolling friction. We concentrate on the particular experimental setup in which the rectangular container has a small "hill" in the middle. Initially all the particles (rough and smooth) are placed on the less steep side, and the dynamics of the particles is followed. With the proper choice of experimental parameters (amplitude and frequency of shaking), segregation can be achieved - all smooth particles cross to the other side of the hill, and most of the rough particles are still bound to their initial side. Theoretically and computationally, not much is known about the motion of a set of hard spherical particles on a surface. While there have been considerable efforts to understand the problem of interaction of a single particle with the substrate
Data Loading...
