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| icc07_-1.pdf | 2007-02-21 15:56:11 | Jeong-Young Ji |
Moment approach to the derivation of general parallel closures
Author: Jeong-Young Ji
Requested Type: Poster Only
Submitted: 2006-12-18 18:45:25
Co-authors: E. D. Held
Contact Info:
Utah State University
Department of Physics
Logan, UT 84322
USA
Abstract Text:
In the moment approach, a general parallel heat flux closure is derived for a stationary plasma with arbitrary collisionalities such as in SSPX experiment. This derivation is an improvement on the previous derivation [E. D. Held et al., Phys. Plasmas 8, 1171(2001)] by using full linearized collision operators [J.-Y. Ji and E. D. Held, Phys. Plasmas 13, 102103 (2006)] instead of pitch-angle scattering operator. The moment approach removes the velocity integral in the integral operator, leaving alone the integration of temperature gradient weighted by exponentially decaying factors along a magnetic field line.
To investigate the quantitative aspects of the closure, it is applied to a sinusoidally varying temperature profile and a monotonically increasing temperature profile with two asymptotic uniform temperature regions. The general closure is compared to the Braginskii diffusive closure and the limitation of the Braginskii closure is quantitatively analyzed. The number of moments for accurate closure calculation depends on the collisionality parametrized as the ratio of the typical gradient scale to the mean free path. This enables one to evaluate the accuracy of fluid closure through truncation of higher moments, and to estimate the number of necessary moments in the truncation closure scheme.
The NIMROD implementation of the general closure is simplified since closure integrals decouple completely. The absence of the velocity integral in the operator allows more freedom in the NIMROD implementation for the integration along the magnetic field line. For a nonstationary plasma with the general acceleration term such as an electric field term, a general scheme of numerical calculations for plasma fluid moments is presented.
Research supported by the U.S. DOE under grant Nos. DE-FG02-04ER54746, DE-FC02-04ER54798 and DE-FC02-05ER54812.
Characterization: E10
Comments:
