An asymptotic-preserving scheme for the kinetic equation with anisotropic scattering

Heavy tail equilibrium and degenerate collision frequency

Li Wang, Bokai Yan

Research output: Contribution to journalArticle

Abstract

We design an asymptotic preserving (AP) scheme for the linear kinetic equation with anisotropic scattering that leads to a fractional diffusion limit. This limit may be attributed to two reasons: A heavy tail equilibrium or a degenerate collision frequency, both of which are considered in this paper. Our scheme builds on the ideas developed in [L. Wang and B. Yan, J. Comput. Phys., 312 (2016), pp. 157-174] but with two major variations. One is a new splitting of the system that accounts for the anisotropy in the scattering cross section by introducing two extra terms. We then showed, via detailed calculation, that the scheme enjoys a relaxed AP property as opposed to the one step AP for the isotropic scattering. Another contribution is for the degenerate collision frequency case, which brings in additional stiffness. We propose to integrate a "body" term, which appears to be the main component in the diffusion limit. This term is precomputed once with a prescribed accuracy, via a change of variable that alleviates the stiffness. Numerical examples are presented to validate its efficiency in both kinetic and fractional diffusion regimes.

Original languageEnglish (US)
Pages (from-to)A422-A451
JournalSIAM Journal on Scientific Computing
Volume41
Issue number1
DOIs
StatePublished - Jan 1 2019

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Heavy Tails
Kinetic Equation
Fractional Diffusion
Diffusion Limit
Collision
Scattering
Kinetics
Stiffness
Term
Change of Variables
Anisotropy
Linear equation
Cross section
Integrate
Numerical Examples

Keywords

  • Anisotropic scattering
  • Asymptotic-preserving scheme
  • Degenerate collision frequency
  • Fractional diffusion
  • Heavy tail equilibrium

Cite this

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title = "An asymptotic-preserving scheme for the kinetic equation with anisotropic scattering: Heavy tail equilibrium and degenerate collision frequency",
abstract = "We design an asymptotic preserving (AP) scheme for the linear kinetic equation with anisotropic scattering that leads to a fractional diffusion limit. This limit may be attributed to two reasons: A heavy tail equilibrium or a degenerate collision frequency, both of which are considered in this paper. Our scheme builds on the ideas developed in [L. Wang and B. Yan, J. Comput. Phys., 312 (2016), pp. 157-174] but with two major variations. One is a new splitting of the system that accounts for the anisotropy in the scattering cross section by introducing two extra terms. We then showed, via detailed calculation, that the scheme enjoys a relaxed AP property as opposed to the one step AP for the isotropic scattering. Another contribution is for the degenerate collision frequency case, which brings in additional stiffness. We propose to integrate a {"}body{"} term, which appears to be the main component in the diffusion limit. This term is precomputed once with a prescribed accuracy, via a change of variable that alleviates the stiffness. Numerical examples are presented to validate its efficiency in both kinetic and fractional diffusion regimes.",
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author = "Li Wang and Bokai Yan",
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T2 - Heavy tail equilibrium and degenerate collision frequency

AU - Wang, Li

AU - Yan, Bokai

PY - 2019/1/1

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N2 - We design an asymptotic preserving (AP) scheme for the linear kinetic equation with anisotropic scattering that leads to a fractional diffusion limit. This limit may be attributed to two reasons: A heavy tail equilibrium or a degenerate collision frequency, both of which are considered in this paper. Our scheme builds on the ideas developed in [L. Wang and B. Yan, J. Comput. Phys., 312 (2016), pp. 157-174] but with two major variations. One is a new splitting of the system that accounts for the anisotropy in the scattering cross section by introducing two extra terms. We then showed, via detailed calculation, that the scheme enjoys a relaxed AP property as opposed to the one step AP for the isotropic scattering. Another contribution is for the degenerate collision frequency case, which brings in additional stiffness. We propose to integrate a "body" term, which appears to be the main component in the diffusion limit. This term is precomputed once with a prescribed accuracy, via a change of variable that alleviates the stiffness. Numerical examples are presented to validate its efficiency in both kinetic and fractional diffusion regimes.

AB - We design an asymptotic preserving (AP) scheme for the linear kinetic equation with anisotropic scattering that leads to a fractional diffusion limit. This limit may be attributed to two reasons: A heavy tail equilibrium or a degenerate collision frequency, both of which are considered in this paper. Our scheme builds on the ideas developed in [L. Wang and B. Yan, J. Comput. Phys., 312 (2016), pp. 157-174] but with two major variations. One is a new splitting of the system that accounts for the anisotropy in the scattering cross section by introducing two extra terms. We then showed, via detailed calculation, that the scheme enjoys a relaxed AP property as opposed to the one step AP for the isotropic scattering. Another contribution is for the degenerate collision frequency case, which brings in additional stiffness. We propose to integrate a "body" term, which appears to be the main component in the diffusion limit. This term is precomputed once with a prescribed accuracy, via a change of variable that alleviates the stiffness. Numerical examples are presented to validate its efficiency in both kinetic and fractional diffusion regimes.

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KW - Asymptotic-preserving scheme

KW - Degenerate collision frequency

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KW - Heavy tail equilibrium

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