2
2.0

Jun 30, 2018
06/18

by
C. L. Ellison; J. W. Burby; J. M. Finn; H. Qin; W. M. Tang

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Backward error initialization and parasitic mode control are well-suited for use in algorithms that arise from a discrete variational principle on phase-space dynamics. Dynamical systems described by degenerate Lagrangians, such as those occurring in phase-space action principles, lead to variational multistep algorithms for the integration of first-order differential equations. As multistep algorithms, an initialization procedure must be chosen and the stability of parasitic modes assessed....

Topics: Physics, Mathematics, Numerical Analysis, Computational Physics

Source: http://arxiv.org/abs/1403.0890

70
70

Sep 21, 2013
09/13

by
J. Squire; H. Qin; W. M. Tang; C. Chandre

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We present a new variational principle for the gyrokinetic system, similar to the Maxwell-Vlasov action presented in Ref. 1. The variational principle is in the Eulerian frame and based on constrained variations of the phase space fluid velocity and particle distribution function. Using a Legendre transform, we explicitly derive the field theoretic Hamiltonian structure of the system. This is carried out with a modified Dirac theory of constraints, which is used to construct meaningful brackets...

Source: http://arxiv.org/abs/1301.6066v2

52
52

Sep 23, 2013
09/13

by
J. A. Baumgaertel; E. A. Belli; W. Dorland; W. Guttenfelder; G. W. Hammett; D. R. Mikkelsen; G. Rewoldt; W. M. Tang; P. Xanthopoulos

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The nonlinear gyrokinetic code GS2 has been extended to treat non-axisymmetric stellarator geometry. Electromagnetic perturbations and multiple trapped particle regions are allowed. Here, linear, collisionless, electrostatic simulations of the quasi-axisymmetric, three-field period National Compact Stellarator Experiment (NCSX) design QAS3-C82 have been successfully benchmarked against the eigenvalue code FULL. Quantitatively, the linear stability calculations of GS2 and FULL agree to within...

Source: http://arxiv.org/abs/1109.4558v1