  Decay of honeycomb-generated turbulence in a duct with a static transverse
magnetic field is studied via direct numerical simulations. The simulations
follow the revealing experimental study of Sukoriansky et al. (1986), in
particular the paradoxical observation of high-amplitude velocity fluctuations,
which exist in the downstream portion of the flow when the strong transverse
magnetic field is imposed in the entire duct including the honeycomb exit, but
not in other configurations. It is shown that the fluctuations are caused by
the large-scale quasi-two-dimensional structures forming in the flow at the
initial stages of the decay and surviving the magnetic suppression. Statistical
turbulence properties, such as the energy decay curves, two-point correlations
and typical length scales are computed. The study demonstrates that turbulence
decay in the presence of a magnetic field is a complex phenomenon critically
depending on the state of the flow at the moment the field is introduced.
