Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ray Effect in Rarefied Flow Simulation   Ray effect usually appears in the radiative transfer when using discrete
ordinates method (DOM) in the simulations. The cause and remedy for the ray
effect have been intensively investigated in the radiation community. For
rarefied gas flow, the ray effect is also associated with the discrete velocity
method (DVM). However, few studies have been carried out in the rarefied
community. In this paper, we take a detailed investigation of the ray effect in
the rarefied flow simulations. Starting from a few commonly used benchmark
tests, the root of the ray effect has been analyzed theoretically and validated
numerically. At the same time, the influence of the ray effect on the quality
of the numerical results of rarefied flow is estimated quantitatively. After
understanding the nature of the ray effect, the strategy to minimize the ray
effect through the discretization of the particle velocity space is presented
and applied in the numerical simulations. An optimal velocity discretization
for DVM is problem dependent and can be hardly obtained in the complex flow
simulations. Due to the intrinsic self-adaptation of particle velocity, the
stochastic particle methods are free from the ray effect. In rarefied regimes,
the particle method seems more appropriate in the capturing of highly
non-equilibrium flow behavior.

19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
37
The categories of this paper are: supr-con
4
The categories of this paper are: cond-mat
12
The categories of this paper are: nucl-th
5
The categories of this paper are: gr-qc