  We present a comprehensive model to account for the behavior of suspended
nanoparticles under magnetohydrodynamic conditions. The Lorentz force not only
drags nanoparticle flocs toward the walls reducing the distance between flocs
resulting a more negative total pair interaction potential energy, but also
produces extra magnetic-induced stresses inside a floc leading to a change of
pair interaction distance thus giving rise to a less negative total potential
energy. The model explains quite well the recent experimental results showing
that magnetic field assists aggregation in laminar or weak turbulent flows, but
favors floc disruption in turbulent regime.
