Helical mode interactions and spectral energy transfer in magnetohydrodynamic turbulence

Spectral transfer processes in magnetohydrodynamic (MHD) turbulence are investigated by decomposition of the velocity and magnetic fields in Fourier space into helical modes. In 1992, Waleffe (Phys. Fluids A, 4:350 (1992)) used this decomposition to calculate triad interactions for isotropic hydrodynamic turbulence and determined whether a given...

Energy spectra and turbulence generation in the wake of magnetic obstacles

Numerical simulations and analysis of flow and heat transfer of an electrically conducting fluid past magnetic obstacles are reported. We studied the channel flow configuration with electrically and thermally insulated horizontal walls containing a single or multiple (two or three) magnetic dipoles. Different values of the interactive parameter...

Electromagnetically driven dwarf tornados in turbulent convection

Motivated by the concept of interdependency of turbulent flow and electromagnetic fields inside the spiraling galaxies, we explored the possibilities of generating a localized Lorentz force that will produce a three-dimensional swirling flow in weakly conductive fluids. Multiple vortical flow patterns were generated by combining arrays of...

Long-term unsteadiness and large-scale structures in Rayleigh-Bénard convection with and without electromagnetic forcing

This dissertation focuses on turbulent thermal convection, which occurs in a wide range of (geo)physical situations, like in the atmosphere, the oceans, the interior of stars or planets, and engineering applications, like metal casting or crystal growth processes. In this work, a special type of thermal convection, Rayleigh-Bénard convection, is...

Modeling and Simulation of Low Voltage Arcs

Modeling and Simulation of Low Voltage Arcs is an attempt to improve the physical understanding, mathematical modeling and numerical simulation of the electric arcs that are found during current interruptions in low voltage circuit breakers. An empirical description is gained by refined electrical measures and fiber optics based imaging. Ways to...

Magnetohydrodynamics of insulating spheres

The effect of electric and magnetic fields on a conducting fluid surrounding an insulating object plays a role in various industrial, biomedical and micro-fluidic applications. Computational simulations of the magnetohydrodynamic flow around an insulating sphere, with crossed magnetic and electric fields perpendicular to the main flow, are...

Magnetohydrodynamics in a finite cylinder: Poloidal-toroidal decomposition

The magnetohydrodynamic equations present two challenging algorithmic requirements: that both fields be solenoidal and that the magnetic field match an unknown external field. The poloidal-toroidal decomposition represents a three-dimensional solenoidal vector field via two scalar potentials. Widely used in Cartesian and spherical geometries...

A Finite Element Interior Penalty Method for MHD in heterogeneous domains

The Maxwell equations in the MHD limit in heterogeneous domains composed of conducting and nonconducting regions are solved by using Lagrange finite elements and by enforcing continuities across interfaces using an interior penalty technique. The method is shown to be stable and convergent and is validated by convergence tests. It is used to...

Magnetohydrodynamics in a domain bounded by a spherical surface: A Fourier-spectral element approximation involving a Dirichlet to Neumann operator for the resolution of the exterior problem

We present a Fourier-spectral element approximation of electromagnetic induction (and magnetohydrodynamics) in a domain bounded by a spherical interface. The electromagnetic problem is cast in terms of electromagnetic potentials, the uniqueness of which is enforced by the choice of Coulomb's gauge. A PN - PN-2 approach ensures the solenoidal...

A direct-numerical-simulation-based second-moment closure for turbulent magnetohydrodynamic flows

A magnetic field, imposed on turbulent flow of an electrically conductive fluid, is known to cause preferential damping of the velocity and its fluctuations in the direction of Lorentz force, thus leading to an increase in stress anisotropy. Based on direct numerical simulations (DNS), we have developed a model of magnetohydrodynamic (MHD)...

A staggered scheme for nonconvex hyperbolic systems of conservation laws