@Article{CiCP-22-157,
author = {Li , Qin and Wang , Li},
title = {Implicit Asymptotic Preserving Method for Linear Transport Equations},
journal = {Communications in Computational Physics},
year = {2019},
volume = {22},
number = {1},
pages = {157--181},
abstract = {<p style="text-align: justify;">The computation of the radiative transfer equation is expensive mainly due
to two stiff terms: the transport term and the collision operator. The stiffness in the
former comes from the fact that particles (such as photons) travel at the speed of light,
while that in the latter is due to the strong scattering in the optically thick region.
We study the fully implicit scheme for this equation to account for the stiffness. The
main challenge in the implicit treatment is the coupling between the spacial and angular coordinates that requires the large size of the to-be-inverted matrix, which is
also ill-conditioned and not necessarily symmetric. Our main idea is to utilize the
spectral structure of the ill-conditioned matrix to construct a pre-conditioner, which,
along with an exquisite split of the spatial and angular dependence, significantly improve the condition number and allows a matrix-free treatment. We also design a fast
solver to compute this pre-conditioner explicitly in advance. Our method is shown
to be efficient in both diffusive and free streaming limit, and the computational cost
is comparable to the state-of-the-art method. Various examples including anisotropic
scattering and two-dimensional problems are provided to validate the effectiveness of
our method.</p>},
issn = {1991-7120},
doi = {https://doi.org/10.4208/cicp.OA-2016-0105},
url = {http://global-sci.org/intro/article_detail/cicp/13351.html}
}