Engineering topics
Wei, L.
Publications and source records attributed to Wei, L..
Synchronization of Geodesic Acoustic Modes and Magnetic Fluctuations in Toroidal Plasmas
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Plasmoid instability in double current sheets
The linear behavior of plasmoid instability in double current sheet configurations, namely, double plasmoid mode (DPM), is analytically and numerically investigated within the framework of a reduced magnetohydrodynamic model. Analytical analysis shows that if the separation of double current sheets is sufficiently small [κx{sub s}≪κ{sup 2/9}S{sub L}{sup 1/3}], the growth rate of DPMs scales as κ{sup 2/3}S{sub L}{sup 0} in the non-constant-ψ regime, where κ=kL{sub CS}/2 is the wave vector measured by the half length of the system L{sub CS}/2, 2x{sub s} is the separation between two resonant surfaces, and S{sub L}=L{sub CS}V{sub A}/2η is Lundquist number with V{sub A} and η being Alfven velocity and resistivity, respectively. If the separation is very large [κx{sub s}≫κ{sup 2/9}S{sub L}{sup 1/3}], the growth rate scales as κ{sup −2/5}S{sub L}{sup 2/5} in the constant-ψ regime. Furthermore, it is also analytically found that the maximum wave number scales as x{sub s}{sup −9/7}S{sub L}{sup 3/7} at the transition position between these two regimes, and the corresponding maximum growth rate scales as x{sub s}{sup −6/7}S{sub L}{sup 2/7} there. The analytically predicted scalings are verified in some limits through direct numerical calculations.
Unstable domains of tearing and Kelvin-Helmholtz instabilities in a rotating cylindrical plasma
Effects of poloidal rotation profile on tearing and Kelvin-Helmholtz (KH) instabilities in a cylindrical plasma are investigated by using a reduced magnetohydrodynamic model. Since the poloidal rotation has different effects on the tearing and KH modes in different rotation regimes, four unstable domains are numerically identified, i.e., the destabilized tearing mode domain, stabilized tearing mode domain, stable-window domain, and unstable KH mode domain. It is also found that when the rotation layer is in the outer region of the rational surface, the stabilizing role of the rotation can be enhanced so significantly that the stable window domain is enlarged. Moreover, Alfvén resonances can be induced by the tearing and KH modes in such rotating plasmas. Radially wide profiles of current and vorticity perturbations can be formed when multiple current sheets on different resonance positions are coupled together.
Model Comparison and Uncertainty Quantification for Geologic Carbon Storage. The Sim-SEQ Initiative
Sim-SEQ is a model comparison initiative for geologic carbon storage (GCS). In Sim-SEQ, fifteen different modeling teams are developing conceptual models for flow and transport of an injected CO 2 plume at the Sim-SEQ study site (or the S-3 site) located near Cranfield, Mississippi. The objective of the project is to understand the sources of model uncertainty in GCS, and if possible, to quantify these uncertainties through comparison of the different conceptual models and also through comparison with observed data from the S-3 site. In this paper, we compare six different conceptual models of the S-3 site, and present a preliminary uncertainty analysis of these six models using a generalized linear model approach. We show that differences in model conceptualization and interpretation of site characterization data caus a significant range in predictions.