We investigate the mixing characteristics of dry granular material whiledraining down a silo with multiple exit orifices. The mixing in the silo, whichotherwise consists of noninteracting stagnant and flow regions, is observed toimprove significantly when the flow through specific orifices is stoppedintermittently. This momentary stoppage of flow through the orifice is eithercontrolled manually or is chosen by the system itself when the orifice width issmall enough to cause spontaneous jamming and unjamming. We observe that theoverall mixing behavior shows a systematic dependence on the frequency ofclosing and opening of specific orifices. In particular, the silo configurationemploying random jamming and unjamming of any of the orifices shows earlyevidence of chaotic mixing. When operated in a multipass mode, the systemexhibits a practical and efficient way of mixing particles.
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