Mixing and Segregation
Liquids have a well-known predisposition for miscibility.1 Dry granular materials, by contrast, are notorious for being difficult to mix homogeneously.2 Two granular materials differing by their density, shape, size, or even by their micromechanical properties (such as coefficient of elastic restitution and friction), exhibit a distinct propensity for segregation. This phenomenon is a fundamental property of the granular state and an unending source of frustration in industry. Whenever a mixture undergoes a flow, a vibration, or a shearing action, the components tend to separate partially or completely, depending on the circumstances. By analogy with chemical reactions, we may say that under the influence of various stimuli a granular mixture inexorably tends to self-organize so as to locally reconstruct clusters of identical particles.
KeywordsGranular Material Rotation Velocity Lattice Line Stable Position Tracer Particle
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