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You searched for subject:(Resistive magnetohydrodynamics). Showing records 1 – 2 of 2 total matches.

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University of Texas – Austin

1. -6327-2527. Hybridized discontinuous Galerkin methods for magnetohydrodynamics.

Degree: PhD, Computational Science, Engineering, and Mathematics, 2018, University of Texas – Austin

Discontinuous Galerkin (DG) methods combine the advantages of classical finite element and finite volume methods. Like finite volume methods, through the use of discontinuous spaces in the discrete functional setting, we automatically have local conservation, an essential property for a numerical method to behave well when applied to hyperbolic conservation laws. Like classical finite element methods, DG methods allow for higher order approximations with compact stencils. For time-dependent problems with implicit time stepping and for steady-state problems, DG methods give a larger globally coupled linear system than continuous Galerkin methods (especially for three dimensional problems and low polynomial orders). The primary motivation of the hybridized (or hybridizable) discontinuous Galerkin (HDG) methods is to reduce the number of globally coupled unknowns in DG methods when implicit time stepping or direct-to-steady-state solutions are desired. This is accomplished by the introduction of new “trace unknowns” defined on the mesh skeleton, the definition of one-sided numerical fluxes, and the enforcement of local conservation. This results in a globally coupled linear system where the local “volume unknowns” can be eliminated in a Schur complement procedure, resulting in a reduced globally coupled system in terms of only the trace unknowns. Magnetohydrodynamics (MHD) is the study of the flow of electrically conducting fluids under the influence of magnetic fields. The MHD equations are used to describe important physical phenomena including laboratory plasmas (plasma confinement in fusion energy devices), astrophysical plasmas (solar coronas, planetary magnetospheres) and liquid metal flows (metallurgy processes, the Earth’s molten core, cooling for nuclear reactors). Incompressible MHD, which is the main focus of this work, is relevant in low Lundquist number liquid metals, in high Lundquist number, large guide field fusion plasmas, and in low Mach number compressible flows. The equations of MHD are highly nonlinear, and are characterized by physical phenomena spanning wide ranges of length and time scales. For numerical methods, this presents challenges in both spatial and temporal discretization. In terms of temporal discretization, fully implicit numerical methods are attractive in their robustness; they allow for stable, high-order time integration over long time scales of interest. Advisors/Committee Members: Bui-Thanh, Tan (advisor), Arbogast, Todd (committee member), Demkowicz, Leszek (committee member), Ghattas, Omar (committee member), Shadid, John (committee member), Waelbroeck, François (committee member).

Subjects/Keywords: Finite element methods; Discontinuous Galerkin methods; Hybridized discontinuous Galerkin methods; Stokes equations; Oseen equations; Magnetohydrodynamics; Resistive magnetohydrodynamics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

-6327-2527. (2018). Hybridized discontinuous Galerkin methods for magnetohydrodynamics. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/2865

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Author name may be incomplete

Chicago Manual of Style (16th Edition):

-6327-2527. “Hybridized discontinuous Galerkin methods for magnetohydrodynamics.” 2018. Doctoral Dissertation, University of Texas – Austin. Accessed January 24, 2021. http://dx.doi.org/10.26153/tsw/2865.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7th Edition):

-6327-2527. “Hybridized discontinuous Galerkin methods for magnetohydrodynamics.” 2018. Web. 24 Jan 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-6327-2527. Hybridized discontinuous Galerkin methods for magnetohydrodynamics. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2018. [cited 2021 Jan 24]. Available from: http://dx.doi.org/10.26153/tsw/2865.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-6327-2527. Hybridized discontinuous Galerkin methods for magnetohydrodynamics. [Doctoral Dissertation]. University of Texas – Austin; 2018. Available from: http://dx.doi.org/10.26153/tsw/2865

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

2. Akramov, Tohir. La reconnexion magnétique explosive dans les nappes de courant multiples : application à l'environnement des pulsars : Explosive magnetic reconnection in multiple current-sheets : application to the environment of pulsars.

Degree: Docteur es, Astrophysique, 2017, Université de Strasbourg

La Nébuleuse du Crabe, contenant en son centre une étoile à neutrons très magnétisée – le pulsar du Crabe, était essentiellement considérée comme une chandelle standard stable dans les rayons-gamma. Récemment, ce point de vue a été contredit par des éruptions en rayons-gamma observées par les satellites spatiaux AGILE/Fermi-LAT. Même si le vent magnétique relativiste du pulsar est considéré comme la source d’énergie, le mécanisme physique à la base de ces événements éruptifs est encore un mystère. Nous avons, dans cette thèse, amélioré la compréhension d’un mécanisme basé sur la reconnexion magnétique rapide, partant du modèle du vent magnétique généré par le pulsar central qui perd son énergie rotationnelle. En effet, la structure du vent magnétique implique la présence des stries à lignes de champ magnétique de polarités alternées (d’où le nom "vent strié") à travers le plan équatorial du pulsar. Dans un modèle simplifié local, nous supposons l’initiation de la dynamique à partir d’une configuration à double nappe de courant (induite par la structure magnétique) dans le repère du vent strié.

The Crab Nebula, containing in its center a highly magnetized neutron star - the Crab pulsar, was essentially considered as a standard steady-state candle in gamma rays. Recently, this point of view has been challenged by gamma-ray flares observed by space satellites AGILE/Fermi-LAT. Even if the relativistic magnetic wind of the pulsar is considered to be the source of energy, the physical mechanism underlying these eruptive events is still a mystery. In this thesis, we improved the understanding of a mechanism based on fast magnetic reconnection, starting from the model of the magnetic wind generated by the central pulsar which loses its rotational kinetic energy. Indeed, the structure of the magnetic wind implies the presence of stripes with magmatic field lines of alternating polarities (hence the name "striped wind") through the equatorial plane of the pulsar. In a simplified local model, we assume the initiation of the dynamics from a double-current sheet configuration (induced by the magnetic structure) in the striped wind reference.

Advisors/Committee Members: Baty, Hubert (thesis director).

Subjects/Keywords: Reconnexion magnétique; Instabilité résistive; Modes de double déchirement; Magnétohydrodynamique; Particules-test; Éruptions de la nébuleuse du Crabe; Magnetic reconnection; Resistive instability; Double-tearing modes; Magnetohydrodynamics; Test-particles; Flares of the Crab nebula; 523.01

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Akramov, T. (2017). La reconnexion magnétique explosive dans les nappes de courant multiples : application à l'environnement des pulsars : Explosive magnetic reconnection in multiple current-sheets : application to the environment of pulsars. (Doctoral Dissertation). Université de Strasbourg. Retrieved from http://www.theses.fr/2017STRAE012

Chicago Manual of Style (16th Edition):

Akramov, Tohir. “La reconnexion magnétique explosive dans les nappes de courant multiples : application à l'environnement des pulsars : Explosive magnetic reconnection in multiple current-sheets : application to the environment of pulsars.” 2017. Doctoral Dissertation, Université de Strasbourg. Accessed January 24, 2021. http://www.theses.fr/2017STRAE012.

MLA Handbook (7th Edition):

Akramov, Tohir. “La reconnexion magnétique explosive dans les nappes de courant multiples : application à l'environnement des pulsars : Explosive magnetic reconnection in multiple current-sheets : application to the environment of pulsars.” 2017. Web. 24 Jan 2021.

Vancouver:

Akramov T. La reconnexion magnétique explosive dans les nappes de courant multiples : application à l'environnement des pulsars : Explosive magnetic reconnection in multiple current-sheets : application to the environment of pulsars. [Internet] [Doctoral dissertation]. Université de Strasbourg; 2017. [cited 2021 Jan 24]. Available from: http://www.theses.fr/2017STRAE012.

Council of Science Editors:

Akramov T. La reconnexion magnétique explosive dans les nappes de courant multiples : application à l'environnement des pulsars : Explosive magnetic reconnection in multiple current-sheets : application to the environment of pulsars. [Doctoral Dissertation]. Université de Strasbourg; 2017. Available from: http://www.theses.fr/2017STRAE012

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