Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Viscoelastic flow transitions in abrupt planar contractions   We present experimental evidence of global viscoelastic flow transitions in
2:1, 8:1 and 32:1 planar contractions under inertia-less conditions. Light
sheet visualization and laser Doppler velocimetry techniques are used to probe
spatial structure and time scales associated with the onset of these
instabilities. The results are reported in terms of critical Weissenberg
numbers characterizing the fluid flow rates. For a given contraction ratio and
polymer fluid, a two-dimensional, steady flow with converging streamlines
transitions to a two-dimensional pattern with diverging streamlines beyond a
critical Weissenberg number. At even higher Weissenberg numbers, spatial
transition to three-dimensional flow is observed. A relationship between the
upstream Weissenberg number for the onset of this spatial instability and the
contraction ratio is derived. For contraction ratios substantially greater than
unity, we observe that further increase in the flow rate results in a second
temporal transition to a three-dimensional, time-dependent flow. This complex
flow arises due to a combination of the effects of stress-curvature interaction
and three dimensional perturbations induced by the walls bounding the neutral
direction. Comparison with studies on other geometries indicates that boundary
shapes deeply influence the sequence and nature of flow transitions.

27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
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The categories of this paper are: patt-sol
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The categories of this paper are: funct-an
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The categories of this paper are: chem-ph
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys