Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: On the generation and destruction mechanisms of arch vortices in urban
  fluid flows
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
37
The categories of this paper are: supr-con
28
The categories of this paper are: alg-geom
23
The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin