ThesisDynamics
of granular segregation
in driven binary monlayers
Manchester Centre for Nonlinear Dynamics
University of Manchester
Supervisor: Tom Mullin
in driven binary monlayers
Manchester Centre for Nonlinear Dynamics
University of Manchester
Supervisor: Tom Mullin
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ABSTRACT: We present results from an experimental investigation of segregation in a binary monolayer of phosphor-bronze spheres and poppy seeds. The particles are driven by the frictional interactions with the surface of a horizontal tray which is forced sinusoidally. Three distinct phases are observed which we classify as binary gas, segregation liquid and segregation crystal. A series of macroscopic and microscopic measures is developed to characterise the phase behaviour of the mixture and analyse its structural configurations. We present evidence for the existence of a continuous phase transition at a critical value of the total filling fraction of the mixture, C'=0.67±0.06. Below Cc the layer remains mixed and for C>Cc segregation domains form. The segregation transition has the typical characteristics of square-root growth of a macroscopic order parameter, critical slowing down and amplification of the microscopic fluctuations. Exploration of the forcing parameter space has also helped uncover a parameter range where segregation is suppressed. The critical value for the dimensionless acceleration of the tray is measured to be g'=2.95±0.16, above which segregation is not observed. We compare our results to an event driven numerical simulation of a 2D phenomenological model of our experimental system and suggest that the segregation is caused by a competition between the differential driving of the two particle species, which induces separation, and random motion, which acts to prevent it.
