Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pore-scale investigation on natural convection melting in a square
  cavity with gradient porous media   In this paper, a numerical study on the melting behavior of phase change
material (PCM) with gradient porous media has been carried out at the pore
scales. In order to solve the governing equations, a pore-scale lattice
Boltzmann method with the double distribution functions is used, in which a
volumetric LB scheme is employed to handle the boundary. The Monte Carlo random
sampling is adopted to generate a microstructure of two-dimensional gradient
foam metal which are then used to simulate the solid-liquid phase transition in
the cavity. The effect of several factors, such as gradient porosity structure,
gradient direction, Rayleigh number and particle diameters on the liquid
fraction of PCM are systematically investigated. It is observed that the
presence of gradient media affect significantly the melting rate and shortens
full melting time compared to that for constant porosity by enhancing natural
convection. The melting time of positive and negative gradients will change
with Rayleigh number, and there is a critical value for Rayleigh number.
Specifically, when Rayleigh number is below the critical value, the positive
gradient is more advantageous, and when Rayleigh number exceeds the critical
value, the negative gradient is more advantageous. Moreover, smaller particle
diameters would lead to lower permeability and larger internal surfaces for
heat transfer.

18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom