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Dynamics of Axial Separation in Long Rotating Drums
| Content Provider | Semantic Scholar |
|---|---|
| Author | Aranson, Igor Tsimring, Lev S. |
| Copyright Year | 1999 |
| Abstract | e f The collective dynamics of granular materials recent have been attracting much interest [1–7]. The dissip tive nature of interaction among macroscopic particl sets granular matter apart from familiar gaseous, liqu or solid states. One of the most fascinating features heterogeneous granular materials is their ability to seg gate under external agitation instead of mixing as wou be expected from thermodynamics. Essentially any var tion in mechanical properties of particles (size, shap density, surface roughness) may lead to their segregati Granular flow in slowly rotating drums is different from conventional fluid motion. In the bulk, particles perform rigid body rotation around the drum axis until they reac the free surface. Then they slide down within a thin nea surface layer [4]. For intermediate rotation speed, the s face has a rather flat S-curved shape, and arctangent o average slope defines the dynamic angle of repose . Since there is almost no interparticle motion in the bulk, se regation of binary granular mixtures predominantly oc curs within the fluidized near-surface layer [3,5,7]. I radial segregation grains of one type (for grains of diffe ent sizes, the smaller ones) build up a core near the a of rotation. It occurs during the first few revolutions o the drum. For long drums, along with radial segregatio axial segregation occurs at much later stages (after hu dreds of revolutions). Recent experiments [3,6,7] r vealed interesting features of axial segregation. For ra rotation speed and large composition fraction of sa grains in a salt-sand mixture f . 0.55, small-scale perturbations travel across the drum at early stages of seg gation. At later times longer-scale perturbations take ov and lead to quasistationary bands of segregated mater which exhibit slow coarsening [5] leading sometimes complete segregation [8]. Most of the theoretical models of segregation agree that the reason for segregation is the sensitive depende of the surface slope or shape on the relative concentrat of different particles in the mixture. In Ref. [6] a simple theory of segregation in thin surface flow driven by th local slope was proposed. For a monodisperse mater the model recovers the S shape of the free surface. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://biocircuits.ucsd.edu/lev/papers/gran/gran2.pdf |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | Axis vertebra Bands Experiment Genetic Heterogeneity Holographic principle Muscle Rigidity Optic axis of a crystal Perturbation theory Radial (radio) Status Epilepticus Sulfanilamide mixture |
| Content Type | Text |
| Resource Type | Article |
