MPEG(*) movies for

Internal Granular Dynamics, Shear-induced Crystallization, and Compaction Steps

-- JC Tsai, G.Voth, and J.Gollub

Internal imaging using index matching, and sensitive volume measurement, are used to investigate the spatial order and dynamics of a deep disordered layer of spheres sheared under a fixed load. Shearing triggers a crystallization transition companied by a step compaction event. The delay preceding the transition depends strongly on layer thickness and can require a translation of about 10^5 particle diameters. The mean velocity varies with depth by more than five decades, and its profile is qualitatively altered by the transition.

d = diameter of glass beads = 0.6mm

Boundary speed = 12 d/s

Thick-layer flows (200g of beads):

    1. Overview: vertical slice of the disordered initial state [2.5Mb, Real-time]

    2. Shear-induced crystallization (vertical slices)

Transition to ordered layers [5.1Mb, ~900X real time] : total length ~ 9 hrs in real time; [Preview: 1.2Mb, ~3600X real time]

Final state [4.7Mb, ~30X real time] : 24 ordered layers 

    3. Horizontal slices at about mid-height:          

Disordered state [4.7Mb, ~30X real time]

Ordered state [4.7Mb, ~30X real time]--> Note the hexagonal structure and occasional defects.

 

Thin-layer flows (vertical slice):

1.Collection of final states[5.1Mb, real-time] created by using different amount of glass beads, from 50g (6 layers) up to 71g.

2.Formation of an ordered state of 6 layers [5.1Mb, real-time].

 

*: Recommended MPEG viewers: IrfanView (providing adjustable playing speeds), Windows Media Player

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