The Dynamics of a Binary Granular Mixture in a Rotating Tube

M.Sc. thesis, unpublished.

Kiam Choo

For this thesis, we studied the dynamics of a binary granular mixture in a rotating tube. Like previous workers, we observed the formation of bands due to the segregation of the two species, as well as the merging and splitting of the bands. In addition, we observed linear travelling waves. We measured the dispersion relation of the travelling waves, and also the velocity dependence on the mixture ratio. The waves stop travelling above a wavelength cutoff and below a mixture ratio cutoff. Near the cutoffs, the travelling waves lose linearity and merge rather than pass through each other. Travelling pulses, sources and possibly sinks were also observed. These results invalidate previous theories on the system. From Fourier analysis of the segregation effect, we were able to determine that the system experiences wavelength selection that is independent of rotation rate, and that the growth in structure varies with rotation rate, and has a peak at about omega = 4 Hz.

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