The transformation of initially isotropic turbulent flow
of electrically conducting incompressible fluid under the influence
of imposed homogeneous magnetic field is investigated using direct
numerical simulation. The limit of low magnetic Reynolds number
is considered. The flow is assumed to be homogeneous and contained in a
three-dimensional cubic box with periodic boundary conditions.
Large-scale forcing is applied to maintain a statistically steady
level of the flow energy.
In the case of strong magnetic field (large
magnetic interaction number) a rapid transformation to purely two-dimensional
steady state is obtained. Due to the type of forcing and boundary conditions
applied this state occurs always in the form of square flow with largest possible
scale. Stability of this flow to three-dimensional perturbations is discussed.