Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Avalanche of particles in evaporating coffee drops   The pioneering work of Deegan et al. [Nature 389, (1997)] showed how a drying
sessile droplet suspension of particles presents a maximum evaporating flux at
its contact line which drags liquid and particles creating the well known
coffee stain ring. In this Fluid Dynamics Video, measurements using micro
Particle Image Velocimetry and Particle Tracking clearly show an avalanche of
particles being dragged in the last moments, for vanishing contact angles and
droplet height. This explains the different characteristic packing of the
particles in the layers of the ring: the outer one resembles a crystalline
array, while the inner one looks more like a jammed granular fluid. Using the
basic hydrodynamic model used by Deegan et al. [Phys. Rev. E 62, (2000)] it
will be shown how the liquid radial velocity diverges as the droplet life comes
to an end, yielding a good comparison with the experimental data.

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The categories of this paper are: cs
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The categories of this paper are: chem-ph
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The categories of this paper are: nlin
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The categories of this paper are: mtrl-th
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The categories of this paper are: quant-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: adap-org
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The categories of this paper are: solv-int
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The categories of this paper are: ao-sci
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-th
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The categories of this paper are: astro-ph
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The categories of this paper are: nucl-ex