201458
20190228220028.0
doi
10.1063/1.4873387
1070-664X
ISI
000337107200029
ARTICLE
Accuracy of momentum and gyrodensity transport in global gyrokinetic particle-in-cell simulations
Melville
Amer Inst Physics
2014
2014
10
Journal Articles
Gyrokinetic Particle-In-Cell (PIC) simulations based on conservative Lagrangian formalisms admit transport equations for conserved quantities such as gyrodensity and toroidal momentum, and these can be derived for arbitrary wavelength, even though previous applications have used the long-wavelength approximation. In control-variate PIC simulations, a consequence of the different treatment of the background (f(0)) and perturbed parts (delta f), when a splitting f = f(0) + delta f is performed, is that analytical transport relations for the relevant fluxes and moments are only reproduced in the large marker number limit. The transport equations for f can be used to write the inconsistency in the perturbed quantities explicitly in terms of the sampling of the background distribution f(0). This immediately allows estimates of the error in consistency of momentum transport in control-variate PIC simulations. This inconsistency tends to accumulate secularly and is not directly affected by the sources and noise control in the system. Although physical tokamaks often rotate quite strongly, the standard gyrokinetic formalism assumes weak perpendicular flows, comparable to the drift speed. For systems with such weak flows, maintaining acceptably small relative errors requires that a number of markers scale with the fourth power of the linear system size to consistently resolve long-wavelength evolution. To avoid this unfavourable scaling, an algorithm for exact gyrodensity transport has been developed, and this is shown to allow accurate simulations with an order of magnitude fewer markers. (C) 2014 AIP Publishing LLC.
Mcmillan, B. F.
Villard, L.
21
5
052501
Physics Of Plasmas
CRPP
252028
SPC
U12272
U12268
U10558
U10635
U12266
U10636
U10137
U12270
U10557
U12273
U10559
U12271
U12269
U12267
U10136
oai:infoscience.tind.io:201458
SB
article
112823
105317
EPFL-ARTICLE-201458
EPFL
REVIEWED
PUBLISHED
ARTICLE