Abstract:
:The motion and mixing of granular media are observed in several contexts in nature, often displaying striking similarities to liquids. Granular dynamics occur in geological phenomena and also enable technologies ranging from pharmaceuticals production to carbon capture. Here, we report the discovery of a family of gravitational instabilities in granular particle mixtures subject to vertical vibration and upward gas flow, including a Rayleigh-Taylor (RT)-like instability in which lighter grains rise through heavier grains in the form of "fingers" and "granular bubbles." We demonstrate that this RT-like instability arises due to a competition between upward drag force increased locally by gas channeling and downward contact forces, and thus the physical mechanism is entirely different from that found in liquids. This gas channeling mechanism also generates other gravitational instabilities: the rise of a granular bubble which leaves a trail of particles behind it and the cascading branching of a descending granular droplet. These instabilities suggest opportunities for patterning within granular mixtures.
journal_name
Proc Natl Acad Sci U S Aauthors
McLaren CP,Kovar TM,Penn A,Müller CR,Boyce CMdoi
10.1073/pnas.1820820116subject
Has Abstractpub_date
2019-05-07 00:00:00pages
9263-9268issue
19eissn
0027-8424issn
1091-6490pii
1820820116journal_volume
116pub_type
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