Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the morphology of two-dimensional laminar vortex streets behind
  triangles   The two-dimensional laminar vortex streets behind a triangle have two
morphologically distinct structures depending on the Reynolds number and the
aspect ratio of the triangle. These two structures are the conventional
structure and the separated rows structure, where the latter is characterized
by a thin layer of irrotational fluid between two vortex rows. In this paper,
by means of numerical simulation, we find that the separated rows structure
occurs when the thickness of boundary layers is less than 25% of their
separation distance. We also show from the linear stability analysis that the
criterion is related to the coupling of two boundary layers in producing
unstable modes.

25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
28
The categories of this paper are: alg-geom
22
The categories of this paper are: chao-dyn
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
4
The categories of this paper are: cond-mat
6
The categories of this paper are: astro-ph