Clustering vs. Declustering


Clustering is a big problem in industrial applications (conveyor belts, sorting machines, etc.), so normally one wants to break these clusters instead of creating them. In order to do so in our experiment, we just have to shake harder.
The pictures below show the break-up of the cluster. Surprisingly, the cluster persists for 42 seconds, and then suddenly (within 1 second) vanishes. This is what we call the sudden death of a granular cluster.

A movie of the clustering experiment can be downloaded here (high-res, 12MB),
and a movie of the sudden death here (high-res, 14MB).



Bidisperse Granular Gas

                                                                     Moderate shaking:


                                                                     Mild shaking:


In a bidisperse granular gas, consisting of large and small particles, the clustering is found to be competitively: it can occur either in a region which originally is populated mainly by small particles or in a region with mainly large particles. The pictures above show the two clustered states occuring at moderate shaking (top row) and mild shaking (bottom row) starting from the same initial state, with the majority of the large ones in the left box, and the majority of the small ones in the right box.
 


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