Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Buoyancy driven bubbly flows: role of meso-scale structures on the
  relative motion between phases, and scaling of velocities in bubble columns
  operated up to the heterogeneous regime
14
The categories of this paper are: math-ph
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
17
The categories of this paper are: q-fin