Accelerated simulation methods for plasma kinetics

Russel Caflisch

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Collisional kinetics is a multiscale phenomenon due to the disparity between the continuum (fluid) and the collisional (particle) length scales. This paper describes a class of simulation methods for gases and plasmas, and acceleration techniques for improving their speed and accuracy. Starting from the Landau-Fokker-Planck equation for plasmas, the focus will be on a binary collision model that is solved using a Direct Simulation Monte Carlo (DSMC) method. Acceleration of this method is achieved by coupling the particle method to a continuum fluid description. The velocity distribution function f is represented as a combination of a Maxwellian M (the thermal component) and a set of discrete particles fp (the kinetic component). For systems that are close to (local) equilibrium, this reduces the number N of simulated particles that are required to represent f for a given level of accuracy. We present two methods for exploiting this representation. In the first method, equilibration of particles in fp, as well as disequilibration of particles from M, due to the collision process, is represented by a thermalization/dethermalization step that employs an entropy criterion. Efficiency of the representation is greatly increased by inclusion of particles with negative weights. This significantly complicates the simulation, but the second method is a tractable approach for negatively weighted particles. The accelerated simulation method is compared with standard PIC-DSMC method for both spatially homogeneous problems such as a bump-on-tail and inhomogeneous problems such as nonlinear Landau damping.

Original languageEnglish (US)
Title of host publication30th International Symposium on Rarefied Gas Dynamics, RGD 2016
EditorsHenning Struchtrup, Andrew Ketsdever
PublisherAmerican Institute of Physics Inc.
ISBN (Electronic)9780735414488
DOIs
StatePublished - Nov 15 2016
Event30th International Symposium on Rarefied Gas Dynamics, RGD 2016 - Victoria, Canada
Duration: Jul 10 2016Jul 15 2016

Publication series

NameAIP Conference Proceedings
Volume1786
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Other

Other30th International Symposium on Rarefied Gas Dynamics, RGD 2016
CountryCanada
CityVictoria
Period7/10/167/15/16

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ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Caflisch, R. (2016). Accelerated simulation methods for plasma kinetics. In H. Struchtrup, & A. Ketsdever (Eds.), 30th International Symposium on Rarefied Gas Dynamics, RGD 2016 [020001] (AIP Conference Proceedings; Vol. 1786). American Institute of Physics Inc.. https://doi.org/10.1063/1.4967537