Magnetohydrodynamic Flows in Arbitrary Geometries in Strong, Nonuniform Magnetic Fields — A Numerical Code for the Design of Fusion Reactor Blankets

1995 ◽  
Vol 27 (1) ◽  
pp. 3-24 ◽  
Author(s):  
L. Bühler
Keyword(s):  
Magnetic Fields ◽  
Fusion Reactor ◽  
Numerical Code ◽  
Magnetohydrodynamic Flows ◽  
Arbitrary Geometries

Periodic imbalances of kinetic and magnetic energies in rotating magnetohydrodynamic turbulent flows

2020 ◽  
Author(s):  
Rustem Sirazov ◽  
Arakel Petrosyan
Keyword(s):  
Magnetic Fields ◽  
Temporal Dynamics ◽  
Wave Packets ◽  
Homogeneous Turbulence ◽  
Initial Time ◽  
The Sun ◽  
Magnetohydrodynamic Turbulence ◽  
The Earth ◽  
Magnetohydrodynamic Flows ◽  
N Wave

<p>A significant number of observed flows in geophysics, astrophysics, and laboratory experiments are in a state of magnetohydrodynamic turbulence. Among them are flows in the Earth’s outer core, in plasma shells of Earth, planets, and satellites of the solar system with strong magnetic fields, as well as flows in the Sun, stars, and astrophysical disks. Despite significant advances in the study of turbulence under the conditions typical of thermonuclear fusion devices, studies of the fundamental properties of homogeneous turbulence in rotating magnetohydrodynamic flows are still fragmentary and mainly concern turbulence in astrophysical disks, the solar tachocline and convective region of the Sun, and two-dimensional magnetohydrodynamic flows on the β-plane. Only in a few exceptional works were the properties of magnetohydrodynamic turbulence studied by simple analytical methods using Fourier series for similarity parameters, characteristic of the Earth’s core.</p><p>The aim of this work is to study the influence of the interaction of Alfvén wave packets on the dynamics of homogeneous turbulence. The method of calculation o magnetohydrodynamic turbulence we developed allows numerical simulation at large characteristic times and large external magnetic fields. The proposed method of setting the initial conditions for the velocity field makes it possible to satisfy the divergence-free, homogeneity, and turbulence isotropy conditions, as well as to set an arbitrary spectral distribution of the energy at the initial time without additional calculations. Numerical experiments demonstrate a nontrivial behavior of turbulent kinetic and magnetic energies. It is shown that periodic imbalance in energies occurs in the system in the form of conversion of kinetic energy into magnetic energy and vice versa. The analysis of the results shows that the detected nontrivial temporal dynamics of turbulence is caused by the periodic collisions of Alfvén wave packets.</p><p>This work was supported by the Russian Foundation for Basic Research (project no. 19-02-00016).</p>

scholarly journals Computing nonlinear force free coronal magnetic fields

2003 ◽  
Vol 10 (4/5) ◽  
pp. 313-322 ◽  
Author(s):  
T. Wiegelmann ◽  
T. Neukirch
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Boundary Conditions ◽  
Random Noise ◽  
Coronal Magnetic Field ◽  
Optimization Method ◽  
Numerical Code ◽  
Coronal Magnetic Fields ◽  
Nonlinear Force ◽  
Free Fields

Abstract. Knowledge of the structure of the coronal magnetic field is important for our understanding of many solar activity phenomena, e.g. flares and CMEs. However, the direct measurement of coronal magnetic fields is not possible with present methods, and therefore the coronal field has to be extrapolated from photospheric measurements. Due to the low plasma beta the coronal magnetic field can usually be assumed to be approximately force free, with electric currents flowing along the magnetic field lines. There are both observational and theoretical reasons which suggest that at least prior to an eruption the coronal magnetic field is in a nonlinear force free state. Unfortunately the computation of nonlinear force free fields is way more difficult than potential or linear force free fields and analytic solutions are not generally available. We discuss several methods which have been proposed to compute nonlinear force free fields and focus particularly on an optimization method which has been suggested recently. We compare the numerical performance of a newly developed numerical code based on the optimization method with the performance of another code based on an MHD relaxation method if both codes are applied to the reconstruction of a semi-analytic nonlinear force-free solution. The optimization method has also been tested for cases where we add random noise to the perfect boundary conditions of the analytic solution, in this way mimicking the more realistic case where the boundary conditions are given by vector magnetogram data. We find that the convergence properties of the optimization method are affected by adding noise to the boundary data and we discuss possibilities to overcome this difficulty.

Thermoelectric magnetohydrodynamics

1979 ◽  
Vol 91 (2) ◽  
pp. 231-251 ◽  
Author(s):  
J. A. Shercliff
Keyword(s):  
Magnetic Fields ◽  
Liquid Metal ◽  
Ab Initio ◽  
Thermoelectric Power ◽  
Thermal Convection ◽  
Thermal Field ◽  
Fusion Reactor ◽  
Nuclear Reactors ◽  
Fusion Reactor Blanket ◽  
Discontinuous Variation

Thermoelectric currents in the presence of magnetic fields can cause pumping or stirring of liquid-metal coolants in nuclear reactors or stirring of molten metal in industrial metallurgy. The interaction between the thermal and magnetohydrodynamic fields is a mutual one owing to alterations in the thermal convection and to the Peltier and Thomson effects (although these are usually small). This paper sets up the equations of magnetohydrodynamics and thermal convection when coupled by thermoelectricity and solves some illustrative problems in which the thermal field is known ab initio. Examples where the effects are due to either continuous or discontinuous variation of material composition are included. Practical magnitudes are discussed for the case of a fusion-reactor blanket, where the effects are potentially important owing to the unusual thermoelectric power of lithium.

Magnetohydrodynamic Flows and Turbulence: a report on the Fourth Beer-Sheva Seminar

1984 ◽  
Vol 148 ◽  
pp. 461-476 ◽  
Author(s):  
H. Branover ◽  
M. Mond ◽  
E. S. Pierson
Keyword(s):  
Power Generation ◽  
Magnetic Fields ◽  
Single Phase ◽  
Nuclear Fission ◽  
Two Phase Flows ◽  
Two Phase ◽  
Beer Sheva ◽  
Mhd Flows ◽  
Magnetohydrodynamic Flows

This paper is a summary of the Fourth Beer-Sheva Seminar on Magnetohydrodynamic (MHD) Flows and Turbulence held in Israel during 27 February–2 March 1984 with 67 participants from 13 countries. Reviews and contributed papers were presented on laminar and turbulent single-phase and two-phase MHD flows, turbulent and two-phase flows without magnetic fields, and applications of MHD in power generation, in nuclear fission and fusion and in metallurgy.

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