  The flow of a simple glass forming system (a 80:20 binary Lennard-Jones
mixture) through a planar channel is studied via molecular dynamics
simulations. The flow is driven by an external body force similar to gravity.
Previous studies show that the model exhibits both a static [Varnik et al. J.
Chem. Phys. 120, 2788 (2004)] and a dynamic [F. Varnik and O. Henrich Phys.
Rev. B 73, 174209 (2006)] yield stress in the glassy phase. \blue{These
observations are corroborated by the present work, where we investigate how the
presence of a yield stress may affect the system behavior in a Poiseuille-type
flow geometry.} In particular, we observe a blunted velocity profile across the
channel: A relatively wide region in the channel center flows with a constant
velocity (zero shear rate) followed by a non linear change of the shear rate as
the walls are approached. The observed velocity gradients are compared to those
obtained from the knowledge of the shear stress across the channel and the
flow-curves (stress versus shear rate), the latter being determined in our
previous simulations of homogeneous shear flow. Furthermore, using the value of
the (dynamic) yield stress known from previous simulations, we estimate the
threshold body force for a complete arrest of the flow. Indeed, a blockage is
observed as the imposed force falls below this threshold value. Small but
finite shear rates are observed at stresses above the dynamic but below the
static yield stress. We discuss the possible role of the \blue{stick-slip like
motion} for this observation.
