Self-diffusion, local clustering and global segregation in binary granular systems: The role of system geometry

Using positron emission particle tracking (PEPT), the influence of system geometry on the dynamical and segregative properties of a three dimensional, vibrofluidised granular system is explored. A relationship between the aspect ratio of a system and the degree of segregation observed is established, demonstrating the ability to adjust segregation intensity within a system simply by modifying its aspect ratio without altering any other parameters, including the number of particles within the system, its volume and the manner in which it is driven. Such a relationship is potentially of value in future research, as well as in industrial settings. The range over which this relationship is valid is determined in terms of the quantity q, the ratio of heating to cooling events within an excited granular system. Within this range, a relationship between self-diffusion, D, and aspect ratio, A, of the form D=αexpβAγ is also proposed. Finally, this study presents what is believed to be the first experimental evidence of sudden chain energy transfer events, a phenomenon recently discovered in two-dimensional granular beds, in a three-dimensional system.