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Author: Hankyu Q. Lee
Requested Type: Poster
Submitted: 2018-03-01 18:34:56

Co-authors: J.A.Spencer, E.D.Held, J.-Y.Ji

Contact Info:
Utah State University
LOGAN, Utah   84322
United States

Abstract Text:
In the general moment approach, a distribution function is expanded in terms of irreducible tensorial Hermite polynomials with coefficients being general moments. The approach is useful to solve kinetic equations in arbitrary collisionality regimes with the help of analytic calculation of collisional moments [1]. Parallel moment equations can be obtained by taking moments of the drift kinetic equation. Truncated sets of equations have been solved for parallel closures with stationary and linear approximations. These parallel closures are expressed as kernel weighted integrals of thermodynamic drives and simple fitted kernels are obtained for arbitrary collisionality [2,3].

In this work, parallel moment equations are implemented in NIMROD. Two different time advance schemes are developed and tested: 1. Consistent with NIMROD's time staggering scheme, odd rank moments are centered with the plasma flow advance and even rank tensor moments are centered with the plasma density and temperatures. 2. All moments are advanced together with implicit scheme to eliminate time-step restrictions. In both cases, convergence and robustness are tested with increasing number of moments. For a stationary case, the parallel moment code is verified by reproducing the integral closures. For a non-stationary case, effects of time-derivative terms on closures are investigated by comparing with the integral closures.

The research is supported by the U.S. DOE under grant nos. DE-SC0014033, DE-SC0016256, and DE-FG02-04ER54746 and was performed in conjunction with the Plasma Science and Innovation (PSI) Center and Center for Tokamak Transient Simulations (CTTS).

[1] J.-Y. Ji and E. D. Held, Phys. Plasmas 13, 102103 (2006).
[2] J.-Y. Ji, S.-K. Kim, E. D. Held, and Y.-S. Na, Phys. Plasmas 23, 032124 (2016).
[3] J.-Y. Ji, H. Q. Lee, and E. D. Held, Phys. Plasmas 24, 022127 (2017).