There is much current academic and technological
interest in separation and pattern formation in vibrated granular systems.
One important mechanism for separation is the influence of a fluid driven
beckwards and forwards through the bed during vibration.
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Under vertical vibration, a mixture of
fine bronze and glass spheres in air separate at lower frequencies with
the heavier bronze uppermost. Download the complete mpeg file here.
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At higher frequencies, the bronze/glass
mixture separates into the sandwich configuration shown above. The
complete mpeg file can be downloaded here.
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Experiment |
Simulation |
Under horizontal vibration, a mixture of
fine bronze/glass spheres in air, or equivalently larger spheres in water,
spontaneously form a striped pattern.
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Between two concentric cylinders, a vertically vibrated mixture of bronze
and glass spheres in water separate and break symmetry to form a heap. The
system further breaks symmetry as the bronze develops different thichnesses
on the two slopes of the heap. The whole system then rotates with the thicker
bronze on the leading edge of the travelling wave.
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