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Description:
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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 . |