Particle Cohesion I

Session Chair:

• Heinrich Jaeger, University of Chicago

Schedule:

Controlling Particle Segregation: Implications of Particle Cohesion, Properties, and Flow Perturbations

Joseph McCarthy, University of Pittsburgh

Segregation, or un-mixing, of particles can be a costly problem and a source of frustration for industries ranging from pharmaceuticals to ceramics to agriculture. When particles differ in almost any mechanical property—size, density, shape, etc.—they become very difficult to keep homogeneous and this problem can even plague "uniform" materials if their is a size or shape distribution within the sample. In this talk, we highlight recent advances in controlling segregation. Specifically, we examine two techniques for segregation control. The first involves using interparticle cohesion, both due to van der Waals forces and/or liquid bridges, either to cause or prevent segregation. The second technique, inspired by fluid mixing, allows us to exploit flow perturbations to limit or even eliminate segregation in free-flowing systems, while at the same time yielding a predictive test-bed for past and future model of segregation kinetics.

Shear Flow of Wet, Flexible Fibers using the Discrete Element Method

Jennifer Curtis, University of Florida

Shear flow of wet and flexible fibers is investigated numerically by means of the Discrete Element Method (DEM). The formation of agglomerates in dilute shear flows is analyzed via the size and coordination number of the agglomerates. A bond number (Bo) is proposed to describe the relative effect of the liquid-bridge force to the particle inertia.  It is found that the sizes of large agglomerates in dilute shear flow are determined by the Bond number. In addition, the effects of particle aspect ratio and fiber flexibility on the agglomerate size and coordination number are examined.  For the dense flow of wet fibers, the effect of the liquid-bridge interaction on the shear stresses is examined.