Magnetohydrodynamic (MHD) investigations of decaying isotropic turbulence
and rectangular jets (RJ) are carried out. A novel MHD lattice Boltzmann scheme that
combines multiple relaxation time (MRT) parameters for the velocity field with a single
relaxation time (SRT) parameter for the Maxwell’s stress tensor is developed for this
study.
In the MHD homogeneous turbulence studies, the kinetic/magnetic energy and
enstrophy decays, kinetic enstrophy evolution, and vorticity alignment with the strain-rate
tensor are evaluated to assess the key physical MHD turbulence mechanisms. The
magnetic and kinetic energies interact and exchange through the influence of the Lorentz
force work. An initial random fluctuating magnetic field increases the vortex stretching
and forward cascade mechanisms. A strong uniform mean magnetic field increases the
anisotropy of the turbulent flow field and causes inverse cascading.
In the RJ studies, an investigation into the MHD effects on velocity, instability,
and the axis-switching phenomena is performed at various magnetic field strengths and
Magnetic Reynolds Numbers. The magnetic field is found to decelerate the jet core,
inhibit instability, and prevent axis-switching. The key physical mechanisms are: (i) the
exchange of energy between kinetic and magnetic modes and (ii) the magnetic field
effect on the vorticity evolution.
From these studies, it is found that magnetic field influences momentum, vorticity,
and energy evolution and the degree of modification depends on the field strength. This
interaction changes vortex evolution, and alters turbulence processes and rectangular jet
flow characteristics. Overall, this study provides more insight into the physics of MHD
flows, which suggests possible applications of MHD Flow Control.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-1222 |
| Date | 15 May 2009 |
| Creators | Riley, Benjamin Matthew |
| Contributors | Girimaji, Sharath S. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | electronic, application/pdf, born digital |
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